diff --git a/cli/tsc/97_ts_host.js b/cli/tsc/97_ts_host.js
index b60574440b3fe0..379affda26a18b 100644
--- a/cli/tsc/97_ts_host.js
+++ b/cli/tsc/97_ts_host.js
@@ -317,6 +317,12 @@ const CACHE_URL_PREFIX = "cache:///";
 /** Diagnostics that are intentionally ignored when compiling TypeScript in
  * Deno, as they provide misleading or incorrect information. */
 const IGNORED_DIAGNOSTICS = [
+  // TS1149: File name '...' differs from already included file name '...' only
+  // in casing.
+  1149,
+  // TS1261: File name '...' differs from already included file name '...' only
+  // in casing.
+  1261,
   // TS1452: 'resolution-mode' assertions are only supported when `moduleResolution` is `node16` or `nodenext`.
   // We specify the resolution mode to be CommonJS for some npm files and this
   // diagnostic gets generated even though we're using custom module resolution.
diff --git a/tests/integration/lsp_tests.rs b/tests/integration/lsp_tests.rs
index 76bb53188e6164..f7e84e4a5e579a 100644
--- a/tests/integration/lsp_tests.rs
+++ b/tests/integration/lsp_tests.rs
@@ -11206,6 +11206,24 @@ fn lsp_root_with_global_reference_types() {
   assert_eq!(json!(diagnostics.all()), json!([]));
 }
 
+#[test]
+#[timeout(300_000)]
+fn lsp_file_casing_no_diagnostic() {
+  let context = TestContextBuilder::new()
+    .use_http_server()
+    .use_temp_cwd()
+    .build();
+  let temp_dir = context.temp_dir();
+  temp_dir.write("other.ts", "");
+  temp_dir.write("Other.ts", "");
+  let file = temp_dir.source_file("file.ts", "import \"./Other.ts\";\n");
+  let mut client = context.new_lsp_command().build();
+  client.initialize_default();
+  // There shouldn't be a TS1149 diagnostic.
+  let diagnostics = client.did_open_file(&file);
+  assert_eq!(json!(diagnostics.all()), json!([]));
+}
+
 #[test]
 #[timeout(300_000)]
 fn lsp_diagnostics_refresh_dependents() {
diff --git a/tests/specs/check/file_casing/Other.ts b/tests/specs/check/file_casing/Other.ts
new file mode 100644
index 00000000000000..e69de29bb2d1d6
diff --git a/tests/specs/check/file_casing/__test__.jsonc b/tests/specs/check/file_casing/__test__.jsonc
new file mode 100644
index 00000000000000..bd4e24338b9317
--- /dev/null
+++ b/tests/specs/check/file_casing/__test__.jsonc
@@ -0,0 +1,4 @@
+{
+  "args": "check --quiet main.ts",
+  "output": ""
+}
diff --git a/tests/specs/check/file_casing/main.ts b/tests/specs/check/file_casing/main.ts
new file mode 100644
index 00000000000000..8d9e5f5eef00e5
--- /dev/null
+++ b/tests/specs/check/file_casing/main.ts
@@ -0,0 +1,2 @@
+import "./other.ts";
+import "./Other.ts";
diff --git a/tests/specs/check/file_casing/other.ts b/tests/specs/check/file_casing/other.ts
new file mode 100644
index 00000000000000..e69de29bb2d1d6