diff --git a/app/build.gradle.kts b/app/build.gradle.kts
index e62a75f9..5ea77adb 100644
--- a/app/build.gradle.kts
+++ b/app/build.gradle.kts
@@ -52,7 +52,7 @@ android {
     buildTypes {
         debug {
             isMinifyEnabled = false
-            buildConfigField("String", "CLODY_BASE_URL", properties["clody.base.url"].toString())
+            buildConfigField("String", "CLODY_BASE_URL", properties["clody.test.url"].toString())
         }
 
         release {
@@ -77,6 +77,11 @@ android {
         buildConfig = true
         compose = true
     }
+    testOptions {
+        unitTests.all {
+            it.useJUnitPlatform()
+        }
+    }
 }
 
 dependencies {
@@ -123,6 +128,11 @@ dependencies {
     // Mavericks
     implementation(libs.bundles.mavericks)
 
+    // Kotest
+    testImplementation(libs.bundles.kotest)
+    testImplementation(libs.mockk)
+    testImplementation(libs.coroutines.test)
+
     // Play Store
     implementation(libs.bundles.plays)
 
diff --git a/app/src/main/java/com/sopt/clody/data/remote/api/DiaryService.kt b/app/src/main/java/com/sopt/clody/data/remote/api/DiaryService.kt
index 8a702f80..bd8981d7 100644
--- a/app/src/main/java/com/sopt/clody/data/remote/api/DiaryService.kt
+++ b/app/src/main/java/com/sopt/clody/data/remote/api/DiaryService.kt
@@ -1,9 +1,11 @@
 package com.sopt.clody.data.remote.api
 
 import com.sopt.clody.data.remote.dto.base.ApiResponse
+import com.sopt.clody.data.remote.dto.request.SaveDraftDiaryRequestDto
 import com.sopt.clody.data.remote.dto.request.WriteDiaryRequestDto
 import com.sopt.clody.data.remote.dto.response.DailyDiariesResponseDto
 import com.sopt.clody.data.remote.dto.response.DiaryTimeResponseDto
+import com.sopt.clody.data.remote.dto.response.DraftDiariesResponseDto
 import com.sopt.clody.data.remote.dto.response.MonthlyCalendarResponseDto
 import com.sopt.clody.data.remote.dto.response.MonthlyDiaryResponseDto
 import com.sopt.clody.data.remote.dto.response.ReplyDiaryResponseDto
@@ -59,4 +61,16 @@ interface DiaryService {
         @Query("month") month: Int,
         @Query("date") date: Int,
     ): ApiResponse<ReplyDiaryResponseDto>
+
+    @GET("api/v1/draft")
+    suspend fun fetchDraftDiary(
+        @Query("year") year: Int,
+        @Query("month") month: Int,
+        @Query("date") date: Int,
+    ): ApiResponse<DraftDiariesResponseDto>
+
+    @POST("api/v1/draft")
+    suspend fun saveDraftDiary(
+        @Body request: SaveDraftDiaryRequestDto,
+    ): ApiResponse<Unit>
 }
diff --git a/app/src/main/java/com/sopt/clody/data/remote/datasource/DiaryRemoteDataSource.kt b/app/src/main/java/com/sopt/clody/data/remote/datasource/DiaryRemoteDataSource.kt
index 19dae1a7..26c0d844 100644
--- a/app/src/main/java/com/sopt/clody/data/remote/datasource/DiaryRemoteDataSource.kt
+++ b/app/src/main/java/com/sopt/clody/data/remote/datasource/DiaryRemoteDataSource.kt
@@ -1,8 +1,10 @@
 package com.sopt.clody.data.remote.datasource
 
 import com.sopt.clody.data.remote.dto.base.ApiResponse
+import com.sopt.clody.data.remote.dto.request.SaveDraftDiaryRequestDto
 import com.sopt.clody.data.remote.dto.response.DailyDiariesResponseDto
 import com.sopt.clody.data.remote.dto.response.DiaryTimeResponseDto
+import com.sopt.clody.data.remote.dto.response.DraftDiariesResponseDto
 import com.sopt.clody.data.remote.dto.response.MonthlyCalendarResponseDto
 import com.sopt.clody.data.remote.dto.response.MonthlyDiaryResponseDto
 import com.sopt.clody.data.remote.dto.response.ReplyDiaryResponseDto
@@ -16,4 +18,6 @@ interface DiaryRemoteDataSource {
     suspend fun getMonthlyCalendarData(year: Int, month: Int): ApiResponse<MonthlyCalendarResponseDto>
     suspend fun getMonthlyDiary(year: Int, month: Int): ApiResponse<MonthlyDiaryResponseDto>
     suspend fun getReplyDiary(year: Int, month: Int, date: Int): ApiResponse<ReplyDiaryResponseDto>
+    suspend fun fetchDraftDiary(year: Int, month: Int, date: Int): ApiResponse<DraftDiariesResponseDto>
+    suspend fun saveDraftDiary(request: SaveDraftDiaryRequestDto): ApiResponse<Unit>
 }
diff --git a/app/src/main/java/com/sopt/clody/data/remote/datasourceimpl/DiaryRemoteDataSourceImpl.kt b/app/src/main/java/com/sopt/clody/data/remote/datasourceimpl/DiaryRemoteDataSourceImpl.kt
index cbbb7b53..f5e35d2a 100644
--- a/app/src/main/java/com/sopt/clody/data/remote/datasourceimpl/DiaryRemoteDataSourceImpl.kt
+++ b/app/src/main/java/com/sopt/clody/data/remote/datasourceimpl/DiaryRemoteDataSourceImpl.kt
@@ -3,9 +3,11 @@ package com.sopt.clody.data.remote.datasourceimpl
 import com.sopt.clody.data.remote.api.DiaryService
 import com.sopt.clody.data.remote.datasource.DiaryRemoteDataSource
 import com.sopt.clody.data.remote.dto.base.ApiResponse
+import com.sopt.clody.data.remote.dto.request.SaveDraftDiaryRequestDto
 import com.sopt.clody.data.remote.dto.request.WriteDiaryRequestDto
 import com.sopt.clody.data.remote.dto.response.DailyDiariesResponseDto
 import com.sopt.clody.data.remote.dto.response.DiaryTimeResponseDto
+import com.sopt.clody.data.remote.dto.response.DraftDiariesResponseDto
 import com.sopt.clody.data.remote.dto.response.MonthlyCalendarResponseDto
 import com.sopt.clody.data.remote.dto.response.MonthlyDiaryResponseDto
 import com.sopt.clody.data.remote.dto.response.ReplyDiaryResponseDto
@@ -35,4 +37,10 @@ class DiaryRemoteDataSourceImpl @Inject constructor(
 
     override suspend fun getReplyDiary(year: Int, month: Int, date: Int): ApiResponse<ReplyDiaryResponseDto> =
         diaryService.getReplyDiary(year = year, month = month, date = date)
+
+    override suspend fun fetchDraftDiary(year: Int, month: Int, date: Int): ApiResponse<DraftDiariesResponseDto> =
+        diaryService.fetchDraftDiary(year = year, month = month, date = date)
+
+    override suspend fun saveDraftDiary(request: SaveDraftDiaryRequestDto): ApiResponse<Unit> =
+        diaryService.saveDraftDiary(request)
 }
diff --git a/app/src/main/java/com/sopt/clody/data/remote/dto/request/SaveDraftDiaryRequestDto.kt b/app/src/main/java/com/sopt/clody/data/remote/dto/request/SaveDraftDiaryRequestDto.kt
new file mode 100644
index 00000000..0fc706af
--- /dev/null
+++ b/app/src/main/java/com/sopt/clody/data/remote/dto/request/SaveDraftDiaryRequestDto.kt
@@ -0,0 +1,10 @@
+package com.sopt.clody.data.remote.dto.request
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+@Serializable
+data class SaveDraftDiaryRequestDto(
+    @SerialName("date") val date: String,
+    @SerialName("draftDiaries") val draftDiaries: List<String>,
+)
diff --git a/app/src/main/java/com/sopt/clody/data/remote/dto/response/DraftDiariesResponseDto.kt b/app/src/main/java/com/sopt/clody/data/remote/dto/response/DraftDiariesResponseDto.kt
new file mode 100644
index 00000000..6bb522b5
--- /dev/null
+++ b/app/src/main/java/com/sopt/clody/data/remote/dto/response/DraftDiariesResponseDto.kt
@@ -0,0 +1,14 @@
+package com.sopt.clody.data.remote.dto.response
+
+import com.sopt.clody.domain.model.DraftDiaryContents
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+@Serializable
+data class DraftDiariesResponseDto(
+    @SerialName("draftDiaries") val draftDiaries: List<String>,
+) {
+    fun toDomain() = DraftDiaryContents(
+        draftDiaries = draftDiaries ?: emptyList(),
+    )
+}
diff --git a/app/src/main/java/com/sopt/clody/data/repositoryimpl/DiaryRepositoryImpl.kt b/app/src/main/java/com/sopt/clody/data/repositoryimpl/DiaryRepositoryImpl.kt
index 20d14634..febe3024 100644
--- a/app/src/main/java/com/sopt/clody/data/repositoryimpl/DiaryRepositoryImpl.kt
+++ b/app/src/main/java/com/sopt/clody/data/repositoryimpl/DiaryRepositoryImpl.kt
@@ -1,6 +1,7 @@
 package com.sopt.clody.data.repositoryimpl
 
 import com.sopt.clody.data.remote.datasource.DiaryRemoteDataSource
+import com.sopt.clody.data.remote.dto.request.SaveDraftDiaryRequestDto
 import com.sopt.clody.data.remote.dto.response.DailyDiariesResponseDto
 import com.sopt.clody.data.remote.dto.response.DiaryTimeResponseDto
 import com.sopt.clody.data.remote.dto.response.MonthlyCalendarResponseDto
@@ -8,6 +9,7 @@ import com.sopt.clody.data.remote.dto.response.MonthlyDiaryResponseDto
 import com.sopt.clody.data.remote.dto.response.ReplyDiaryResponseDto
 import com.sopt.clody.data.remote.dto.response.WriteDiaryResponseDto
 import com.sopt.clody.data.remote.util.handleApiResponse
+import com.sopt.clody.domain.model.DraftDiaryContents
 import com.sopt.clody.domain.repository.DiaryRepository
 import com.sopt.clody.presentation.utils.network.ErrorMessages
 import com.sopt.clody.presentation.utils.network.ErrorMessages.FAILURE_TEMPORARY_MESSAGE
@@ -80,4 +82,21 @@ class DiaryRepositoryImpl @Inject constructor(
             }
             response
         }
+
+    override suspend fun fetchDraftDiary(year: Int, month: Int, date: Int): Result<DraftDiaryContents> =
+        runCatching {
+            diaryRemoteDataSource
+                .fetchDraftDiary(year, month, date)
+                .handleApiResponse()
+                .getOrThrow()
+                .toDomain()
+        }
+
+    override suspend fun saveDraftDiary(date: String, contents: List<String>): Result<Unit> =
+        runCatching {
+            diaryRemoteDataSource
+                .saveDraftDiary(SaveDraftDiaryRequestDto(date = date, draftDiaries = contents))
+                .handleApiResponse()
+                .getOrThrow()
+        }
 }
diff --git a/app/src/main/java/com/sopt/clody/domain/model/DraftDiaryContents.kt b/app/src/main/java/com/sopt/clody/domain/model/DraftDiaryContents.kt
new file mode 100644
index 00000000..45ddcbd1
--- /dev/null
+++ b/app/src/main/java/com/sopt/clody/domain/model/DraftDiaryContents.kt
@@ -0,0 +1,5 @@
+package com.sopt.clody.domain.model
+
+data class DraftDiaryContents(
+    val draftDiaries: List<String>,
+)
diff --git a/app/src/main/java/com/sopt/clody/domain/repository/DiaryRepository.kt b/app/src/main/java/com/sopt/clody/domain/repository/DiaryRepository.kt
index 9c95565e..3666ed18 100644
--- a/app/src/main/java/com/sopt/clody/domain/repository/DiaryRepository.kt
+++ b/app/src/main/java/com/sopt/clody/domain/repository/DiaryRepository.kt
@@ -6,6 +6,7 @@ import com.sopt.clody.data.remote.dto.response.MonthlyCalendarResponseDto
 import com.sopt.clody.data.remote.dto.response.MonthlyDiaryResponseDto
 import com.sopt.clody.data.remote.dto.response.ReplyDiaryResponseDto
 import com.sopt.clody.data.remote.dto.response.WriteDiaryResponseDto
+import com.sopt.clody.domain.model.DraftDiaryContents
 
 interface DiaryRepository {
     suspend fun writeDiary(date: String, content: List<String>): Result<WriteDiaryResponseDto>
@@ -15,4 +16,6 @@ interface DiaryRepository {
     suspend fun getMonthlyCalendarData(year: Int, month: Int): Result<MonthlyCalendarResponseDto>
     suspend fun getMonthlyDiary(year: Int, month: Int): Result<MonthlyDiaryResponseDto>
     suspend fun getReplyDiary(year: Int, month: Int, date: Int): Result<ReplyDiaryResponseDto>
+    suspend fun fetchDraftDiary(year: Int, month: Int, date: Int): Result<DraftDiaryContents>
+    suspend fun saveDraftDiary(date: String, contents: List<String>): Result<Unit>
 }
diff --git a/app/src/main/java/com/sopt/clody/domain/usecase/FetchDraftDiaryUseCase.kt b/app/src/main/java/com/sopt/clody/domain/usecase/FetchDraftDiaryUseCase.kt
new file mode 100644
index 00000000..929c2e1f
--- /dev/null
+++ b/app/src/main/java/com/sopt/clody/domain/usecase/FetchDraftDiaryUseCase.kt
@@ -0,0 +1,13 @@
+package com.sopt.clody.domain.usecase
+
+import com.sopt.clody.domain.model.DraftDiaryContents
+import com.sopt.clody.domain.repository.DiaryRepository
+import javax.inject.Inject
+
+class FetchDraftDiaryUseCase @Inject constructor(
+    private val repository: DiaryRepository,
+) {
+    suspend operator fun invoke(year: Int, month: Int, day: Int): Result<DraftDiaryContents> {
+        return repository.fetchDraftDiary(year, month, day)
+    }
+}
diff --git a/app/src/main/java/com/sopt/clody/domain/usecase/SaveDraftDiaryUseCase.kt b/app/src/main/java/com/sopt/clody/domain/usecase/SaveDraftDiaryUseCase.kt
new file mode 100644
index 00000000..a1b2ffa6
--- /dev/null
+++ b/app/src/main/java/com/sopt/clody/domain/usecase/SaveDraftDiaryUseCase.kt
@@ -0,0 +1,12 @@
+package com.sopt.clody.domain.usecase
+
+import com.sopt.clody.domain.repository.DiaryRepository
+import javax.inject.Inject
+
+class SaveDraftDiaryUseCase @Inject constructor(
+    private val diaryRepository: DiaryRepository,
+) {
+    suspend operator fun invoke(date: String, contents: List<String>): Result<Unit> {
+        return diaryRepository.saveDraftDiary(date, contents)
+    }
+}
diff --git a/app/src/main/java/com/sopt/clody/presentation/ui/component/dialog/ClodyDialog.kt b/app/src/main/java/com/sopt/clody/presentation/ui/component/dialog/ClodyDialog.kt
index 6d45a195..c0846c94 100644
--- a/app/src/main/java/com/sopt/clody/presentation/ui/component/dialog/ClodyDialog.kt
+++ b/app/src/main/java/com/sopt/clody/presentation/ui/component/dialog/ClodyDialog.kt
@@ -43,6 +43,7 @@ fun ClodyDialog(
     confirmButtonColor: Color,
     confirmButtonTextColor: Color,
     onDismiss: () -> Unit,
+    onDismissButtonClick: (() -> Unit)? = null,
 ) {
     var isButtonClicked by remember { mutableStateOf(false) }
 
@@ -68,8 +69,7 @@ fun ClodyDialog(
                     .wrapContentHeight(),
             ) {
                 Column(
-                    modifier = Modifier
-                        .padding(28.dp),
+                    modifier = Modifier.padding(28.dp),
                     horizontalAlignment = Alignment.CenterHorizontally,
                     verticalArrangement = Arrangement.Center,
                 ) {
@@ -92,21 +92,21 @@ fun ClodyDialog(
                     Spacer(modifier = Modifier.height(32.dp))
 
                     Row(
-                        modifier = Modifier
-                            .fillMaxWidth(),
+                        modifier = Modifier.fillMaxWidth(),
                     ) {
                         Button(
                             onClick = {
                                 if (!isButtonClicked) {
                                     isButtonClicked = true
-                                    onDismiss()
+                                    // dismiss 버튼 클릭 시: 우선순위는 onDismissButtonClick
+                                    onDismissButtonClick?.invoke() ?: onDismiss()
                                 }
                             },
                             modifier = Modifier
                                 .weight(1f)
                                 .background(
                                     color = ClodyTheme.colors.gray07,
-                                    shape = RoundedCornerShape(size = 8.dp),
+                                    shape = RoundedCornerShape(8.dp),
                                 ),
                             colors = ButtonDefaults.buttonColors(ClodyTheme.colors.gray07),
                         ) {
@@ -130,7 +130,7 @@ fun ClodyDialog(
                                 .weight(1f)
                                 .background(
                                     color = confirmButtonColor,
-                                    shape = RoundedCornerShape(size = 8.dp),
+                                    shape = RoundedCornerShape(8.dp),
                                 ),
                             colors = ButtonDefaults.buttonColors(confirmButtonColor),
                         ) {
diff --git a/app/src/main/java/com/sopt/clody/presentation/ui/writediary/component/textfield/WriteDiaryTextField.kt b/app/src/main/java/com/sopt/clody/presentation/ui/writediary/component/textfield/WriteDiaryTextField.kt
index e3a24cde..e2593bde 100644
--- a/app/src/main/java/com/sopt/clody/presentation/ui/writediary/component/textfield/WriteDiaryTextField.kt
+++ b/app/src/main/java/com/sopt/clody/presentation/ui/writediary/component/textfield/WriteDiaryTextField.kt
@@ -163,7 +163,7 @@ fun WriteDiaryTextField(
                     .fillMaxWidth()
                     .padding(start = 8.dp, top = 6.dp),
             ) {
-                if ((showWarning && !isTextValid && text.isNotEmpty()) || isTextTooLong) {
+                if ((showWarning && !isTextValid) || isTextTooLong) {
                     Text(
                         text = "2~50자 까지 입력할 수 있어요.",
                         color = ClodyTheme.colors.red,
diff --git a/app/src/main/java/com/sopt/clody/presentation/ui/writediary/screen/WriteDiaryScreen.kt b/app/src/main/java/com/sopt/clody/presentation/ui/writediary/screen/WriteDiaryScreen.kt
index da7ec6bd..3af5e77e 100644
--- a/app/src/main/java/com/sopt/clody/presentation/ui/writediary/screen/WriteDiaryScreen.kt
+++ b/app/src/main/java/com/sopt/clody/presentation/ui/writediary/screen/WriteDiaryScreen.kt
@@ -1,5 +1,6 @@
 package com.sopt.clody.presentation.ui.writediary.screen
 
+import androidx.activity.compose.BackHandler
 import androidx.compose.foundation.background
 import androidx.compose.foundation.clickable
 import androidx.compose.foundation.interaction.MutableInteractionSource
@@ -48,6 +49,7 @@ import com.sopt.clody.presentation.utils.amplitude.AmplitudeConstraints
 import com.sopt.clody.presentation.utils.amplitude.AmplitudeUtils
 import com.sopt.clody.presentation.utils.base.BasePreview
 import com.sopt.clody.presentation.utils.base.ClodyPreview
+import com.sopt.clody.presentation.utils.extension.LaunchedEffectWhenStarted
 import com.sopt.clody.presentation.utils.extension.getDayOfWeek
 import com.sopt.clody.presentation.utils.extension.heightForScreenPercentage
 import com.sopt.clody.ui.theme.ClodyTheme
@@ -74,6 +76,10 @@ fun WriteDiaryRoute(
     val showDialog by viewModel::showDialog
     val showExitDialog by viewModel::showExitDialog
 
+    LaunchedEffectWhenStarted {
+        viewModel.fetchDraftDiary(year, month, date)
+    }
+
     LaunchedEffect(writeDiaryState) {
         when (writeDiaryState) {
             is WriteDiaryState.Success -> navigateToReplyLoading(year, month, date)
@@ -83,6 +89,19 @@ fun WriteDiaryRoute(
         }
     }
 
+    BackHandler {
+        if (showExitDialog) {
+            viewModel.updateShowExitDialog(false)
+        } else {
+            if (viewModel.hasChangedFromInitial()) {
+                AmplitudeUtils.trackEvent(AmplitudeConstraints.WRITING_DIARY_BACK)
+                viewModel.updateShowExitDialog(true)
+            } else {
+                navigateToPrevious()
+            }
+        }
+    }
+
     WriteDiaryScreen(
         isLoading = writeDiaryState is WriteDiaryState.Loading,
         entries = entries,
@@ -95,7 +114,7 @@ fun WriteDiaryRoute(
         failureMessage = failureMessage,
         showExitDialog = showExitDialog,
         onClickBack = {
-            if (entries.any { it.isNotBlank() }) {
+            if (viewModel.hasChangedFromInitial()) {
                 AmplitudeUtils.trackEvent(AmplitudeConstraints.WRITING_DIARY_BACK)
                 viewModel.updateShowExitDialog(true)
             } else {
@@ -138,9 +157,11 @@ fun WriteDiaryRoute(
         onDismissLimitMessage = { viewModel.updateShowLimitMessage(false) },
         onDismissEmptyFieldsMessage = { viewModel.updateShowEmptyFieldsMessage(false) },
         onDismissFailureDialog = { viewModel.resetFailureDialog() },
+        onDismiss = { viewModel.updateShowExitDialog(false) },
         onDismissExitDialog = {
             viewModel.updateDraftUsage()
             viewModel.updateShowExitDialog(false)
+            viewModel.saveDraftDiary(year, month, date)
             navigateToHome(year, month)
         },
         onConfirmExitDialog = {
@@ -177,6 +198,7 @@ fun WriteDiaryScreen(
     failureMessage: String,
     showExitDialog: Boolean,
     onDismissFailureDialog: () -> Unit,
+    onDismiss: () -> Unit,
     onDismissExitDialog: () -> Unit,
     onConfirmExitDialog: () -> Unit,
     year: Int,
@@ -285,7 +307,8 @@ fun WriteDiaryScreen(
                             confirmAction = onConfirmExitDialog,
                             confirmButtonColor = ClodyTheme.colors.red,
                             confirmButtonTextColor = ClodyTheme.colors.white,
-                            onDismiss = onDismissExitDialog,
+                            onDismiss = onDismiss,
+                            onDismissButtonClick = onDismissExitDialog,
                         )
                     }
                 }
@@ -382,6 +405,7 @@ private fun WriteDiaryScreenPreview() {
             failureMessage = "",
             showExitDialog = false,
             onDismissFailureDialog = {},
+            onDismiss = {},
             onDismissExitDialog = {},
             onConfirmExitDialog = {},
             year = 2023,
diff --git a/app/src/main/java/com/sopt/clody/presentation/ui/writediary/screen/WriteDiaryViewModel.kt b/app/src/main/java/com/sopt/clody/presentation/ui/writediary/screen/WriteDiaryViewModel.kt
index c1818f07..5b27cbc1 100644
--- a/app/src/main/java/com/sopt/clody/presentation/ui/writediary/screen/WriteDiaryViewModel.kt
+++ b/app/src/main/java/com/sopt/clody/presentation/ui/writediary/screen/WriteDiaryViewModel.kt
@@ -10,6 +10,9 @@ import androidx.lifecycle.viewModelScope
 import com.sopt.clody.data.remote.util.NetworkUtil
 import com.sopt.clody.domain.repository.DiaryRepository
 import com.sopt.clody.domain.repository.DraftRepository
+import com.sopt.clody.domain.usecase.FetchDraftDiaryUseCase
+import com.sopt.clody.domain.usecase.SaveDraftDiaryUseCase
+import com.sopt.clody.presentation.utils.network.ErrorMessages
 import com.sopt.clody.presentation.utils.network.ErrorMessages.FAILURE_NETWORK_MESSAGE
 import com.sopt.clody.presentation.utils.network.ErrorMessages.FAILURE_TEMPORARY_MESSAGE
 import com.sopt.clody.presentation.utils.network.ErrorMessages.UNKNOWN_ERROR
@@ -22,6 +25,8 @@ import javax.inject.Inject
 @HiltViewModel
 class WriteDiaryViewModel @Inject constructor(
     private val diaryRepository: DiaryRepository,
+    private val fetchDraftDiaryUseCase: FetchDraftDiaryUseCase,
+    private val saveDraftDiaryUseCase: SaveDraftDiaryUseCase,
     private val networkUtil: NetworkUtil,
     private val draftRepository: DraftRepository,
 ) : ViewModel() {
@@ -59,6 +64,8 @@ class WriteDiaryViewModel @Inject constructor(
     var showExitDialog by mutableStateOf(false)
         private set
 
+    private var initialEntries: List<String> = emptyList()
+
     fun writeDiary(year: Int, month: Int, day: Int, contents: List<String>) {
         viewModelScope.launch {
             if (!networkUtil.isNetworkAvailable()) {
@@ -171,6 +178,55 @@ class WriteDiaryViewModel @Inject constructor(
         showExitDialog = show
     }
 
+    fun hasChangedFromInitial(): Boolean {
+        return entries != initialEntries
+    }
+
+    fun fetchDraftDiary(year: Int, month: Int, day: Int) {
+        viewModelScope.launch {
+            _entries.clear()
+            _showWarnings.clear()
+
+            val result = fetchDraftDiaryUseCase(year, month, day)
+            result.onSuccess { response ->
+                val drafts = response.draftDiaries.ifEmpty { listOf("") }
+                _entries.addAll(drafts)
+                initialEntries = drafts.toList()
+
+                _showWarnings.addAll(List(_entries.size) { false })
+                checkLimitMessage()
+                checkEmptyFieldsMessage()
+            }.onFailure {
+                ensureDefaultEntry()
+                _failureMessage.value = ErrorMessages.FETCH_TEMP_DIARY_FAILED
+                _showFailureDialog.value = true
+            }
+        }
+    }
+
+    fun saveDraftDiary(year: Int, month: Int, day: Int) {
+        viewModelScope.launch {
+            val date = String.format("%04d-%02d-%02d", year, month, day)
+            val result = saveDraftDiaryUseCase(date, _entries.toList())
+            result.onSuccess {
+                _failureMessage.value = ""
+                _showFailureDialog.value = false
+            }.onFailure { e ->
+                _failureMessage.value = e.localizedMessage ?: UNKNOWN_ERROR
+                _showFailureDialog.value = true
+            }
+        }
+    }
+
+    private fun ensureDefaultEntry() {
+        _entries.clear()
+        _entries.add("")
+        _showWarnings.clear()
+        _showWarnings.add(false)
+        checkLimitMessage()
+        checkEmptyFieldsMessage()
+    }
+
     fun updateDraftUsage() {
         if (!draftRepository.getIsDraftUsed()) {
             draftRepository.setIsDraftUsed(true)
diff --git a/app/src/main/java/com/sopt/clody/presentation/utils/extension/LifeCycle.kt b/app/src/main/java/com/sopt/clody/presentation/utils/extension/LifeCycle.kt
index 61458078..8e0208ab 100644
--- a/app/src/main/java/com/sopt/clody/presentation/utils/extension/LifeCycle.kt
+++ b/app/src/main/java/com/sopt/clody/presentation/utils/extension/LifeCycle.kt
@@ -1,7 +1,10 @@
 package com.sopt.clody.presentation.utils.extension
 
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
 import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.LifecycleOwner
+import androidx.lifecycle.compose.LocalLifecycleOwner
 import androidx.lifecycle.lifecycleScope
 import androidx.lifecycle.repeatOnLifecycle
 import kotlinx.coroutines.CoroutineScope
@@ -25,3 +28,28 @@ fun LifecycleOwner.repeatOnStarted(block: suspend CoroutineScope.() -> Unit) {
         lifecycle.repeatOnLifecycle(Lifecycle.State.STARTED, block)
     }
 }
+
+/**
+ * [LifecycleOwner]가 [lifecycleState] 이상일 때만 [block]을 실행하는 [LaunchedEffect] 기반의 Composable 유틸함수.
+ * 내부적으로 [Lifecycle.repeatOnLifecycle]을 사용하여 생명주기 안전성을 보장.
+ * SideEffect 처리를 lifecycle-aware하게 실행하고 싶을 때 사용하면 됨.
+ *
+ * @param key [LaunchedEffect]를 트리거할 key. 일반적으로 의존성이 되는 상태나 객체.
+ * @param lifecycleState 반복 실행을 시작할 최소 생명주기 상태 (기본값: STARTED)
+ * @param block 지정한 생명주기 상태 이상일 때만 실행할 suspend 블록
+ */
+
+@Composable
+fun LaunchedEffectWhenStarted(
+    key: Any? = Unit,
+    lifecycleState: Lifecycle.State = Lifecycle.State.STARTED,
+    block: suspend CoroutineScope.() -> Unit,
+) {
+    val lifecycleOwner = LocalLifecycleOwner.current
+
+    LaunchedEffect(key, lifecycleOwner) {
+        lifecycleOwner.lifecycle.repeatOnLifecycle(lifecycleState) {
+            block()
+        }
+    }
+}
diff --git a/app/src/main/java/com/sopt/clody/presentation/utils/network/ErrorMessages.kt b/app/src/main/java/com/sopt/clody/presentation/utils/network/ErrorMessages.kt
index 3aa8a1a2..3db50f7e 100644
--- a/app/src/main/java/com/sopt/clody/presentation/utils/network/ErrorMessages.kt
+++ b/app/src/main/java/com/sopt/clody/presentation/utils/network/ErrorMessages.kt
@@ -4,5 +4,6 @@ object ErrorMessages {
     const val FAILURE_NETWORK_MESSAGE = "서비스 접속이 원활하지 않아요.\n네트워크 연결을 확인해주세요."
     const val FAILURE_TEMPORARY_MESSAGE = "일시적인 오류가 발생했어요.\n잠시 후 다시 시도해주세요."
     const val FAILURE_SERVER_MESSAGE = "서버 오류가 발생했어요.\n잠시 후 다시 시도해주세요."
+    const val FETCH_TEMP_DIARY_FAILED = "임시저장 불러오기에 실패했어요.\n잠시 후 다시 시도해주세요."
     const val UNKNOWN_ERROR = "알수없는 에러"
 }
diff --git a/app/src/test/java/com/sopt/clody/FakeDiaryRepository.kt b/app/src/test/java/com/sopt/clody/FakeDiaryRepository.kt
new file mode 100644
index 00000000..9355bd74
--- /dev/null
+++ b/app/src/test/java/com/sopt/clody/FakeDiaryRepository.kt
@@ -0,0 +1,55 @@
+package com.sopt.clody
+
+import com.sopt.clody.data.remote.dto.response.DailyDiariesResponseDto
+import com.sopt.clody.data.remote.dto.response.DiaryTimeResponseDto
+import com.sopt.clody.data.remote.dto.response.MonthlyCalendarResponseDto
+import com.sopt.clody.data.remote.dto.response.MonthlyDiaryResponseDto
+import com.sopt.clody.data.remote.dto.response.ReplyDiaryResponseDto
+import com.sopt.clody.data.remote.dto.response.WriteDiaryResponseDto
+import com.sopt.clody.domain.model.CreatedDraftDiaryInfo
+import com.sopt.clody.domain.model.DraftDiaryContents
+import com.sopt.clody.domain.repository.DiaryRepository
+
+class FakeDiaryRepository : DiaryRepository {
+    var draftDiaryResult: Result<DraftDiaryContents>? = null
+    var saveDraftResult: Result<CreatedDraftDiaryInfo>? = null
+    private var draftDiaryContents: DraftDiaryContents? = null
+
+    override suspend fun writeDiary(date: String, content: List<String>): Result<WriteDiaryResponseDto> {
+        throw NotImplementedError("This method is not implemented in FakeDiaryRepository")
+    }
+
+    override suspend fun deleteDailyDiary(year: Int, month: Int, day: Int): Result<DailyDiariesResponseDto> {
+        throw NotImplementedError("This method is not implemented in FakeDiaryRepository")
+    }
+
+    override suspend fun getDailyDiariesData(year: Int, month: Int, date: Int): Result<DailyDiariesResponseDto> {
+        throw NotImplementedError("This method is not implemented in FakeDiaryRepository")
+    }
+
+    override suspend fun getDiaryTime(year: Int, month: Int, date: Int): Result<DiaryTimeResponseDto> {
+        throw NotImplementedError("This method is not implemented in FakeDiaryRepository")
+    }
+
+    override suspend fun getMonthlyCalendarData(year: Int, month: Int): Result<MonthlyCalendarResponseDto> {
+        throw NotImplementedError("This method is not implemented in FakeDiaryRepository")
+    }
+
+    override suspend fun getMonthlyDiary(year: Int, month: Int): Result<MonthlyDiaryResponseDto> {
+        throw NotImplementedError("This method is not implemented in FakeDiaryRepository")
+    }
+
+    override suspend fun getReplyDiary(year: Int, month: Int, date: Int): Result<ReplyDiaryResponseDto> {
+        throw NotImplementedError("This method is not implemented in FakeDiaryRepository")
+    }
+
+    override suspend fun fetchDraftDiary(year: Int, month: Int, date: Int): Result<DraftDiaryContents> {
+        return draftDiaryContents?.let { Result.success(it) }
+            ?: Result.failure(IllegalStateException("No draft found"))
+    }
+
+    override suspend fun saveDraftDiary(contents: List<String>): Result<CreatedDraftDiaryInfo> {
+        draftDiaryContents = DraftDiaryContents(contents)
+        return Result.success(CreatedDraftDiaryInfo(createdAt = "2024-06-01T00:00:00"))
+    }
+}
diff --git a/app/src/test/java/com/sopt/clody/WriteDiaryViewModelTest.kt b/app/src/test/java/com/sopt/clody/WriteDiaryViewModelTest.kt
new file mode 100644
index 00000000..31c1a2bc
--- /dev/null
+++ b/app/src/test/java/com/sopt/clody/WriteDiaryViewModelTest.kt
@@ -0,0 +1,86 @@
+package com.sopt.clody
+
+import com.sopt.clody.domain.model.CreatedDraftDiaryInfo
+import com.sopt.clody.domain.model.DraftDiaryContents
+import com.sopt.clody.domain.usecase.FetchDraftDiaryUseCase
+import com.sopt.clody.domain.usecase.SaveDraftDiaryUseCase
+import com.sopt.clody.presentation.ui.writediary.screen.WriteDiaryViewModel
+import io.kotest.assertions.nondeterministic.eventually
+import io.kotest.core.spec.style.BehaviorSpec
+import io.kotest.matchers.collections.shouldContainExactly
+import io.kotest.matchers.shouldBe
+import io.mockk.mockk
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.UnconfinedTestDispatcher
+import kotlinx.coroutines.test.resetMain
+import kotlinx.coroutines.test.setMain
+import kotlin.time.Duration.Companion.seconds
+
+@OptIn(ExperimentalCoroutinesApi::class)
+class WriteDiaryViewModelTest : BehaviorSpec(
+    {
+
+        val testDispatcher = UnconfinedTestDispatcher()
+
+        beforeTest {
+            Dispatchers.setMain(testDispatcher)
+        }
+
+        afterTest {
+            Dispatchers.resetMain()
+        }
+
+        Given("fetchDraftDiary 호출 시") {
+            val mockContents = listOf("entry1", "entry2", "entry3")
+            val fakeRepo = FakeDiaryRepository().apply {
+                draftDiaryResult = Result.success(DraftDiaryContents(mockContents))
+            }
+
+            val viewModel = WriteDiaryViewModel(
+                diaryRepository = fakeRepo,
+                fetchDraftDiaryUseCase = FetchDraftDiaryUseCase(fakeRepo),
+                saveDraftDiaryUseCase = SaveDraftDiaryUseCase(fakeRepo),
+                networkUtil = mockk(relaxed = true),
+            )
+
+            When("fetchDraftDiaryUseCase가 성공하면") {
+                viewModel.fetchDraftDiary(2025, 6, 1)
+
+                Then("entries와 showWarnings가 초기화된다") {
+                    eventually(duration = 2.seconds) {
+                        viewModel.entries shouldContainExactly mockContents
+                        viewModel.showWarnings shouldContainExactly List(mockContents.size) { false }
+                    }
+                }
+            }
+        }
+
+        Given("saveDraftDiary 호출 시") {
+            val fakeRepo = FakeDiaryRepository().apply {
+                saveDraftResult = Result.success(CreatedDraftDiaryInfo("2025-06-01T00:00:00.000Z"))
+            }
+
+            val viewModel = WriteDiaryViewModel(
+                diaryRepository = fakeRepo,
+                fetchDraftDiaryUseCase = FetchDraftDiaryUseCase(fakeRepo),
+                saveDraftDiaryUseCase = SaveDraftDiaryUseCase(fakeRepo),
+                networkUtil = mockk(relaxed = true),
+            )
+
+            viewModel.updateEntry(0, "entry1")
+            viewModel.addEntry()
+            viewModel.updateEntry(1, "entry2")
+
+            viewModel.saveDraftDiary()
+
+            Then("에러 메시지가 설정되지 않는다") {
+                eventually(duration = 3.seconds) {
+                    viewModel.showFailureDialog.value shouldBe false
+                    viewModel.failureMessage.value shouldBe ""
+                    println("dialog = ${viewModel.showFailureDialog.value}, message = ${viewModel.failureMessage.value}")
+                }
+            }
+        }
+    },
+)
diff --git a/app/src/test/java/com/sopt/clody/datasource/FakeDiaryRemoteDataSource.kt b/app/src/test/java/com/sopt/clody/datasource/FakeDiaryRemoteDataSource.kt
new file mode 100644
index 00000000..4829638c
--- /dev/null
+++ b/app/src/test/java/com/sopt/clody/datasource/FakeDiaryRemoteDataSource.kt
@@ -0,0 +1,78 @@
+package com.sopt.clody.datasource
+
+import com.sopt.clody.data.remote.datasource.DiaryRemoteDataSource
+import com.sopt.clody.data.remote.dto.base.ApiResponse
+import com.sopt.clody.data.remote.dto.request.SaveDraftDiaryRequestDto
+import com.sopt.clody.data.remote.dto.response.DailyDiariesResponseDto
+import com.sopt.clody.data.remote.dto.response.DiaryTimeResponseDto
+import com.sopt.clody.data.remote.dto.response.DraftDiariesResponseDto
+import com.sopt.clody.data.remote.dto.response.MonthlyCalendarResponseDto
+import com.sopt.clody.data.remote.dto.response.MonthlyDiaryResponseDto
+import com.sopt.clody.data.remote.dto.response.ReplyDiaryResponseDto
+import com.sopt.clody.data.remote.dto.response.WriteDiaryResponseDto
+
+class FakeDiaryRemoteDataSource : DiaryRemoteDataSource {
+
+    var draftDiariesResponse: ApiResponse<DraftDiariesResponseDto>? = null
+    var saveDraftResponse: ApiResponse<Unit>? = null
+
+    override suspend fun writeDiary(date: String, content: List<String>): ApiResponse<WriteDiaryResponseDto> {
+        throw NotImplementedError()
+    }
+
+    override suspend fun deleteDailyDiary(year: Int, month: Int, date: Int): ApiResponse<DailyDiariesResponseDto> {
+        throw NotImplementedError()
+    }
+
+    override suspend fun getDailyDiariesData(year: Int, month: Int, date: Int): ApiResponse<DailyDiariesResponseDto> {
+        throw NotImplementedError()
+    }
+
+    override suspend fun getDiaryTime(year: Int, month: Int, date: Int): ApiResponse<DiaryTimeResponseDto> {
+        throw NotImplementedError()
+    }
+
+    override suspend fun getMonthlyCalendarData(year: Int, month: Int): ApiResponse<MonthlyCalendarResponseDto> {
+        throw NotImplementedError()
+    }
+
+    override suspend fun getMonthlyDiary(year: Int, month: Int): ApiResponse<MonthlyDiaryResponseDto> {
+        throw NotImplementedError()
+    }
+
+    override suspend fun getReplyDiary(year: Int, month: Int, date: Int): ApiResponse<ReplyDiaryResponseDto> {
+        throw NotImplementedError()
+    }
+
+    override suspend fun fetchDraftDiary(
+        year: Int,
+        month: Int,
+        date: Int,
+    ): ApiResponse<DraftDiariesResponseDto> {
+        return draftDiariesResponse
+            ?: throw IllegalStateException("draftDiariesResponse not set")
+    }
+
+    override suspend fun saveDraftDiary(
+        request: SaveDraftDiaryRequestDto,
+    ): ApiResponse<Unit> {
+        return saveDraftResponse
+            ?: throw IllegalStateException("saveDraftResponse not set")
+    }
+
+    fun setDraftDiariesResponse(list: List<String>) {
+        draftDiariesResponse = ApiResponse(
+            status = 200,
+            message = "성공",
+            data = DraftDiariesResponseDto(draftDiaries = list),
+        )
+    }
+
+    fun setSaveDraftDiaryResponse(createdAt: String) {
+        saveDraftResponse = ApiResponse(
+            status = 201,
+            message = "성공",
+            data = Unit,
+        )
+    }
+}
diff --git a/app/src/test/java/com/sopt/clody/repositoryimpl/DiaryRepositoryImplTest.kt b/app/src/test/java/com/sopt/clody/repositoryimpl/DiaryRepositoryImplTest.kt
new file mode 100644
index 00000000..6acd516d
--- /dev/null
+++ b/app/src/test/java/com/sopt/clody/repositoryimpl/DiaryRepositoryImplTest.kt
@@ -0,0 +1,59 @@
+package com.sopt.clody.repositoryimpl
+
+import com.sopt.clody.data.repositoryimpl.DiaryRepositoryImpl
+import com.sopt.clody.datasource.FakeDiaryRemoteDataSource
+import io.kotest.core.spec.style.BehaviorSpec
+import io.kotest.matchers.shouldBe
+
+class DiaryRepositoryImplTest : BehaviorSpec({
+
+    Given("임시저장 다이어리 조회 기능") {
+
+        val fakeDiaryRemoteDataSource = FakeDiaryRemoteDataSource()
+        val diaryRepository = DiaryRepositoryImpl(fakeDiaryRemoteDataSource)
+
+        When("유효한 날짜를 전달받으면") {
+
+            Then("해당 날짜의 임시저장 데이터를 정상적으로 반환한다") {
+                // arrange
+                val mockData = listOf("오늘도 고생했어", "하루 정리 완료")
+                fakeDiaryRemoteDataSource.setDraftDiariesResponse(mockData)
+
+                // act
+                val result = diaryRepository.fetchDraftDiary(2025, 5, 31)
+
+                // assert
+                println("fetchDraftDiary result: $result")
+                println("fetchDraftDiary error: ${result.exceptionOrNull()?.message}")
+
+                result.isSuccess shouldBe true
+                result.getOrNull()?.draftDiaries shouldBe mockData
+            }
+        }
+    }
+
+    Given("임시저장 다이어리 저장 기능") {
+
+        val fakeDiaryRemoteDataSource = FakeDiaryRemoteDataSource()
+        val diaryRepository = DiaryRepositoryImpl(fakeDiaryRemoteDataSource)
+
+        When("유효한 데이터로 저장 요청을 하면") {
+
+            Then("정상적으로 저장된 시간 정보를 반환한다") {
+                // arrange
+                val createdAt = "2025-05-31T20:43:20.696606"
+                fakeDiaryRemoteDataSource.setSaveDraftDiaryResponse(createdAt)
+
+                // act
+                val result = diaryRepository.saveDraftDiary(listOf("Test"))
+
+                // assert
+                println("saveDraftDiary result: $result")
+                println("saveDraftDiary error: ${result.exceptionOrNull()?.message}")
+
+                result.isSuccess shouldBe true
+                result.getOrNull()?.createdAt shouldBe createdAt
+            }
+        }
+    }
+},)
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index fb65e83e..1e3c001a 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -47,8 +47,9 @@ accompanist = "0.25.1"
 accompanist-insets = "0.28.0"
 
 firebase-config-ktx = "22.1.0"
-
 mavericks = "3.0.9"
+kotestVersion = "5.9.0"
+mockk = "1.13.10"
 
 play-review = "2.0.2"
 
@@ -124,6 +125,13 @@ mavericks = { module = "com.airbnb.android:mavericks", version.ref = "mavericks"
 mavericks-compose = { module = "com.airbnb.android:mavericks-compose", version.ref = "mavericks" }
 mavericks-hilt = { module = "com.airbnb.android:mavericks-hilt", version.ref = "mavericks" }
 
+# Kotest
+kotest-runner = { group = "io.kotest", name = "kotest-runner-junit5", version.ref = "kotestVersion" }
+kotest-assertions = { group = "io.kotest", name = "kotest-assertions-core", version.ref = "kotestVersion" }
+kotest-property = { group = "io.kotest", name = "kotest-property", version.ref = "kotestVersion" }
+
+mockk = { group = "io.mockk", name = "mockk", version.ref = "mockk" }
+
 # PlayStore In App Review
 play-review = { group = "com.google.android.play", name = "review", version.ref = "play-review"}
 play-review-ktx = { group = "com.google.android.play", name = "review-ktx", version.ref = "play-review"}
@@ -165,7 +173,6 @@ test = [
     "androidx-junit",
     "espresso-core",
     "ui-test-junit4",
-    "coroutines-test"
 ]
 
 debug = [
@@ -200,6 +207,12 @@ mavericks = [
     "mavericks-hilt"
 ]
 
+kotest = [
+    "kotest-runner",
+    "kotest-assertions",
+    "kotest-property"
+]
+
 plays = [
     "play-review",
     "play-review-ktx"