diff --git a/meshroom/core/graph.py b/meshroom/core/graph.py
index a2039e72f1..2b789f96a2 100644
--- a/meshroom/core/graph.py
+++ b/meshroom/core/graph.py
@@ -223,6 +223,7 @@ def __init__(self, name, parent=None):
         self._compatibilityNodes = DictModel(keyAttrName='name', parent=self)
         self.cacheDir = meshroom.core.defaultCacheFolder
         self._filepath = ''
+        self._fileDateVersion = 0
         self.header = {}
 
     def clear(self):
@@ -267,6 +268,8 @@ def load(self, filepath, setupProjectFile=True, importProject=False, publishOutp
 
         if not isinstance(graphData, dict):
             raise RuntimeError('loadGraph error: Graph is not a dict. File: {}'.format(filepath))
+        
+        self._fileDateVersion = os.path.getmtime(filepath)
 
         self.header = fileData.get(Graph.IO.Keys.Header, {})
         nodesVersions = self.header.get(Graph.IO.Keys.NodesVersions, {})
@@ -1539,6 +1542,18 @@ def cacheDir(self, value):
         self.updateStatusFromCache(force=True)
         self.cacheDirChanged.emit()
 
+    @property
+    def fileDateVersion(self):
+        return self._fileDateVersion
+    
+    @fileDateVersion.setter
+    def fileDateVersion(self, value):
+        self._fileDateVersion = value
+
+    @Slot(str, result=float)
+    def getFileDateVersionFromPath(self, value):
+        return os.path.getmtime(value)
+
     def setVerbose(self, v):
         with GraphModification(self):
             for node in self._nodes:
@@ -1553,6 +1568,7 @@ def setVerbose(self, v):
     filepathChanged = Signal()
     filepath = Property(str, lambda self: self._filepath, notify=filepathChanged)
     fileReleaseVersion = Property(str, lambda self: self.header.get(Graph.IO.Keys.ReleaseVersion, "0.0"), notify=filepathChanged)
+    fileDateVersion = Property(float, fileDateVersion.fget, fileDateVersion.fset, notify=filepathChanged)
     cacheDirChanged = Signal()
     cacheDir = Property(str, cacheDir.fget, cacheDir.fset, notify=cacheDirChanged)
     updated = Signal()
diff --git a/meshroom/ui/qml/main.qml b/meshroom/ui/qml/main.qml
index fb707e3b35..a896d6dd6e 100644
--- a/meshroom/ui/qml/main.qml
+++ b/meshroom/ui/qml/main.qml
@@ -368,6 +368,36 @@ ApplicationWindow {
             onDiscarded: close()
             onAccepted: saveAsAction.trigger()
         }
+
+        MessageDialog {
+            id: fileModifiedDialog
+
+            canCopy: false
+            icon.text: MaterialIcons.warning
+            parent: Overlay.overlay
+            preset: "Warning"
+            title: "File Modified"
+            text: "The file has been modified by another instance."
+            detailedText: "Do you want to overwrite the file?"
+
+            // Add a reload file button next to the save button
+            footer: DialogButtonBox {
+                position: DialogButtonBox.Footer
+                standardButtons: Dialog.Save | Dialog.Cancel
+                
+                Button {
+                    text: "Reload File"
+
+                    onClicked: {
+                        _reconstruction.loadUrl(_reconstruction.graph.filepath)
+                        fileModifiedDialog.close()
+                    }
+                }
+            }
+
+            onAccepted: _reconstruction.save()
+            onDiscarded: close()
+        }
     }
 
     FileDialog {
@@ -715,7 +745,14 @@ ApplicationWindow {
                 enabled: _reconstruction ? (_reconstruction.graph && !_reconstruction.graph.filepath) || !_reconstruction.undoStack.clean : false
                 onTriggered: {
                     if (_reconstruction.graph.filepath) {
-                        _reconstruction.save()
+                        // get current time date
+                        var date = _reconstruction.graph.getFileDateVersionFromPath(_reconstruction.graph.filepath)
+
+                        // check if the file has been modified by another instance
+                        if (_reconstruction.graph.fileDateVersion !== date) {
+                            fileModifiedDialog.open()
+                        } else
+                            _reconstruction.save()
                     } else {
                         initFileDialogFolder(saveFileDialog)
                         saveFileDialog.open()
diff --git a/meshroom/ui/reconstruction.py b/meshroom/ui/reconstruction.py
index 951267da16..afb1e2f45b 100755
--- a/meshroom/ui/reconstruction.py
+++ b/meshroom/ui/reconstruction.py
@@ -509,6 +509,8 @@ def load(self, filepath, setupProjectFile=True, publishOutputs=False):
                     "Data might have been lost in the process.",
                     "Open it with the corresponding version of Meshroom to recover your data."
                 ))
+            
+            self.graph.fileDateVersion = os.path.getmtime(filepath)
             return status
         except FileNotFoundError as e:
             self.error.emit(