diff --git a/FatPkg/EnhancedFatDxe/Delete.c b/FatPkg/EnhancedFatDxe/Delete.c
index 448d669f9d..2c84b5282a 100644
--- a/FatPkg/EnhancedFatDxe/Delete.c
+++ b/FatPkg/EnhancedFatDxe/Delete.c
@@ -31,6 +31,10 @@ FatDelete (
   EFI_STATUS  Status;
   UINTN       Round;
 
+  if (FeaturePcdGet (PcdFatReadOnlyMode)) {
+    return EFI_WRITE_PROTECTED;
+  }
+
   IFile = IFILE_FROM_FHAND (FHand);
   OFile = IFile->OFile;
 
diff --git a/FatPkg/EnhancedFatDxe/DirectoryManage.c b/FatPkg/EnhancedFatDxe/DirectoryManage.c
index 723fc35f38..d296033b13 100644
--- a/FatPkg/EnhancedFatDxe/DirectoryManage.c
+++ b/FatPkg/EnhancedFatDxe/DirectoryManage.c
@@ -73,6 +73,10 @@ FatStoreDirEnt (
   UINT8              EntryCount;
   UINT8              LfnOrdinal;
 
+  if (FeaturePcdGet (PcdFatReadOnlyMode)) {
+    return EFI_WRITE_PROTECTED;
+  }
+
   EntryPos   = DirEnt->EntryPos;
   EntryCount = DirEnt->EntryCount;
   //
@@ -709,6 +713,9 @@ FatExpandODir (
   IN FAT_OFILE  *OFile
   )
 {
+  if (FeaturePcdGet (PcdFatReadOnlyMode)) {
+    return EFI_WRITE_PROTECTED;
+  }
   return FatExpandOFile (OFile, OFile->FileSize + OFile->Volume->ClusterSize);
 }
 
@@ -954,6 +961,10 @@ FatSetVolumeEntry (
   FAT_DIRENT  LabelDirEnt;
   FAT_OFILE   *Root;
 
+  if (FeaturePcdGet (PcdFatReadOnlyMode)) {
+    return EFI_WRITE_PROTECTED;
+  }
+
   Root   = Volume->Root;
   Status = FatSeekVolumeId (Volume->Root, &LabelDirEnt);
   if (EFI_ERROR (Status)) {
@@ -1001,6 +1012,10 @@ FatCreateDotDirEnts (
   EFI_STATUS  Status;
   FAT_DIRENT  *DirEnt;
 
+  if (FeaturePcdGet (PcdFatReadOnlyMode)) {
+    return EFI_WRITE_PROTECTED;
+  }
+
   Status = FatExpandODir (OFile);
   if (EFI_ERROR (Status)) {
     return Status;
@@ -1048,6 +1063,10 @@ FatCreateDirEnt (
   FAT_ODIR    *ODir;
   EFI_STATUS  Status;
 
+  if (FeaturePcdGet (PcdFatReadOnlyMode)) {
+    return EFI_WRITE_PROTECTED;
+  }
+
   ASSERT (OFile != NULL);
   ODir = OFile->ODir;
   ASSERT (ODir != NULL);
@@ -1105,6 +1124,10 @@ FatRemoveDirEnt (
 {
   FAT_ODIR  *ODir;
 
+  if (FeaturePcdGet (PcdFatReadOnlyMode)) {
+    return EFI_WRITE_PROTECTED;
+  }
+
   ODir = OFile->ODir;
   if (ODir->CurrentCursor == &DirEnt->Link) {
     //
diff --git a/FatPkg/EnhancedFatDxe/FileSpace.c b/FatPkg/EnhancedFatDxe/FileSpace.c
index 909d4980d2..d1573df5fb 100644
--- a/FatPkg/EnhancedFatDxe/FileSpace.c
+++ b/FatPkg/EnhancedFatDxe/FileSpace.c
@@ -362,6 +362,10 @@ FatShrinkEof (
   UINTN       Cluster;
   UINTN       LastCluster;
 
+  if (FeaturePcdGet (PcdFatReadOnlyMode)) {
+    return EFI_WRITE_PROTECTED;
+  }
+
   Volume = OFile->Volume;
   ASSERT_VOLUME_LOCKED (Volume);
 
@@ -440,6 +444,10 @@ FatGrowEof (
   UINTN       NewCluster;
   UINTN       ClusterCount;
 
+  if (FeaturePcdGet (PcdFatReadOnlyMode)) {
+    return EFI_WRITE_PROTECTED;
+  }
+
   //
   // For FAT file system, the max file is 4GB.
   //
diff --git a/FatPkg/EnhancedFatDxe/Flush.c b/FatPkg/EnhancedFatDxe/Flush.c
index 8c6010328b..294641e798 100644
--- a/FatPkg/EnhancedFatDxe/Flush.c
+++ b/FatPkg/EnhancedFatDxe/Flush.c
@@ -35,6 +35,10 @@ FatFlushEx (
   EFI_STATUS  Status;
   FAT_TASK    *Task;
 
+  if (FeaturePcdGet (PcdFatReadOnlyMode)) {
+    return EFI_WRITE_PROTECTED;
+  }
+
   IFile  = IFILE_FROM_FHAND (FHand);
   OFile  = IFile->OFile;
   Volume = OFile->Volume;
@@ -112,6 +116,9 @@ FatFlush (
   IN EFI_FILE_PROTOCOL  *FHand
   )
 {
+  if (FeaturePcdGet (PcdFatReadOnlyMode)) {
+    return EFI_WRITE_PROTECTED;
+  }
   return FatFlushEx (FHand, NULL);
 }
 
diff --git a/FatPkg/EnhancedFatDxe/ReadWrite.c b/FatPkg/EnhancedFatDxe/ReadWrite.c
index 8f525044d1..cf0ed0f52b 100644
--- a/FatPkg/EnhancedFatDxe/ReadWrite.c
+++ b/FatPkg/EnhancedFatDxe/ReadWrite.c
@@ -211,6 +211,10 @@ FatIFileAccess (
   UINT64      EndPosition;
   FAT_TASK    *Task;
 
+  if (FeaturePcdGet (PcdFatReadOnlyMode) && IoMode == WriteData) {
+    return EFI_WRITE_PROTECTED;
+  }
+
   IFile  = IFILE_FROM_FHAND (FHand);
   OFile  = IFile->OFile;
   Volume = OFile->Volume;
@@ -414,6 +418,9 @@ FatWrite (
   IN     VOID               *Buffer
   )
 {
+  if (FeaturePcdGet (PcdFatReadOnlyMode)) {
+    return EFI_WRITE_PROTECTED;
+  }
   return FatIFileAccess (FHand, WriteData, BufferSize, Buffer, NULL);
 }
 
@@ -437,6 +444,9 @@ FatWriteEx (
   IN OUT EFI_FILE_IO_TOKEN  *Token
   )
 {
+  if (FeaturePcdGet (PcdFatReadOnlyMode)) {
+    return EFI_WRITE_PROTECTED;
+  }
   return FatIFileAccess (FHand, WriteData, &Token->BufferSize, Token->Buffer, Token);
 }
 
@@ -471,6 +481,10 @@ FatAccessOFile (
   EFI_STATUS  Status;
   UINTN       BufferSize;
 
+  if (FeaturePcdGet (PcdFatReadOnlyMode) && IoMode == WriteData) {
+    return EFI_WRITE_PROTECTED;
+  }
+
   BufferSize = *DataBufferSize;
   Volume     = OFile->Volume;
   ASSERT_VOLUME_LOCKED (Volume);
@@ -542,6 +556,10 @@ FatExpandOFile (
   EFI_STATUS  Status;
   UINTN       WritePos;
 
+  if (FeaturePcdGet (PcdFatReadOnlyMode)) {
+    return EFI_WRITE_PROTECTED;
+  }
+
   WritePos = OFile->FileSize;
   Status   = FatGrowEof (OFile, ExpandedSize);
   if (!EFI_ERROR (Status)) {
@@ -575,6 +593,10 @@ FatWriteZeroPool (
   UINTN       BufferSize;
   UINTN       WriteSize;
 
+  if (FeaturePcdGet (PcdFatReadOnlyMode)) {
+    return EFI_WRITE_PROTECTED;
+  }
+
   AppendedSize = OFile->FileSize - WritePos;
   BufferSize   = AppendedSize;
   if (AppendedSize > FAT_MAX_ALLOCATE_SIZE) {
@@ -624,6 +646,10 @@ FatTruncateOFile (
   IN UINTN      TruncatedSize
   )
 {
+  if (FeaturePcdGet (PcdFatReadOnlyMode)) {
+    return EFI_WRITE_PROTECTED;
+  }
+
   OFile->FileSize = TruncatedSize;
   return FatShrinkEof (OFile);
 }