diff --git a/media/gpu/windows/media_foundation_video_encode_accelerator_win.cc b/media/gpu/windows/media_foundation_video_encode_accelerator_win.cc
index 6ac97542f6e04..2953b5420b6f1 100644
--- a/media/gpu/windows/media_foundation_video_encode_accelerator_win.cc
+++ b/media/gpu/windows/media_foundation_video_encode_accelerator_win.cc
@@ -3111,6 +3111,15 @@ HRESULT MediaFoundationVideoEncodeAccelerator::PerformD3DCopy(
     D3D11_TEXTURE2D_DESC input_desc;
     input_texture->GetDesc(&input_desc);
 
+    // CopySubresourceRegion requires that the source and destination formats
+    // be identical or in the same type group, otherwise the runtime silently
+    // drops the copy and the destination retains its uninitialized contents.
+    if (input_desc.Format != DXGI_FORMAT_NV12) {
+      LOG(ERROR) << "Source texture format " << input_desc.Format
+                 << " is not compatible with NV12 destination";
+      return E_INVALIDARG;
+    }
+
     if (visible_rect.x() < 0 || visible_rect.y() < 0 ||
         visible_rect.right() > static_cast<int>(input_desc.Width) ||
         visible_rect.bottom() > static_cast<int>(input_desc.Height)) {
diff --git a/media/gpu/windows/media_foundation_video_encode_accelerator_win_unittest.cc b/media/gpu/windows/media_foundation_video_encode_accelerator_win_unittest.cc
index a2bf2a13b4a77..57c4513dd24d5 100644
--- a/media/gpu/windows/media_foundation_video_encode_accelerator_win_unittest.cc
+++ b/media/gpu/windows/media_foundation_video_encode_accelerator_win_unittest.cc
@@ -292,10 +292,10 @@ TEST_P(MediaFoundationVideoEncodeAcceleratorAlignmentTest,
             EncoderStatus::Codes::kInvalidInputFrame);
 }
 
-class MediaFoundationVideoEncodeAcceleratorKeyedMutexTimeoutTest
+class MediaFoundationVideoEncodeAcceleratorD3DCopyTest
     : public ::testing::Test {
  public:
-  MediaFoundationVideoEncodeAcceleratorKeyedMutexTimeoutTest() = default;
+  MediaFoundationVideoEncodeAcceleratorD3DCopyTest() = default;
 
   void SetUp() override {
     mock_d3d11_device_ = Microsoft::WRL::Make<D3D11DeviceMock>();
@@ -378,7 +378,7 @@ class MediaFoundationVideoEncodeAcceleratorKeyedMutexTimeoutTest
 // Tests that if the keyed mutex cannot be acquired (e.g. returns WAIT_TIMEOUT),
 // the encoder drops the frame and signals an error instead of silently
 // proceeding and encoding uninitialized GPU VRAM.
-TEST_F(MediaFoundationVideoEncodeAcceleratorKeyedMutexTimeoutTest,
+TEST_F(MediaFoundationVideoEncodeAcceleratorD3DCopyTest,
        RejectFrameOnKeyedMutexTimeout) {
   // 1. Set up a mock keyed mutex that simulates a WAIT_TIMEOUT scenario.
   auto mock_keyed_mutex = Microsoft::WRL::Make<DXGIKeyedMutexMock>();
@@ -451,6 +451,62 @@ TEST_F(MediaFoundationVideoEncodeAcceleratorKeyedMutexTimeoutTest,
   task_environment_.RunUntilIdle();
 }
 
+// Tests that if the source texture has a format that is not compatible with
+// the NV12 destination, the encoder rejects the frame instead of issuing a
+// CopySubresourceRegion call that the D3D runtime would silently drop.
+TEST_F(MediaFoundationVideoEncodeAcceleratorD3DCopyTest,
+       RejectMismatchedSourceTextureFormat) {
+  // 1. Set up a mock texture whose description reports a non-NV12 format. No
+  // keyed mutex is provided so the format check is exercised directly.
+  auto mock_texture =
+      Microsoft::WRL::Make<MockD3D11Texture2D>(mock_d3d11_device_);
+
+  D3D11_TEXTURE2D_DESC desc = {};
+  gfx::Size input_visible_size(1280, 720);
+  desc.Width = input_visible_size.width();
+  desc.Height = input_visible_size.height();
+  desc.Format = DXGI_FORMAT_B8G8R8A8_UNORM;
+  EXPECT_CALL(*mock_texture.Get(), GetDesc(_))
+      .WillRepeatedly([desc](D3D11_TEXTURE2D_DESC* pDesc) { *pDesc = desc; });
+
+  // 2. Setup the mock D3D11 device to return our mock texture when opening the
+  // shared resource.
+  EXPECT_CALL(*mock_d3d11_device_.Get(), OpenSharedResource1(_, _, _))
+      .WillOnce([&mock_texture](HANDLE, REFIID riid, void** ppv) {
+        return mock_texture.CopyTo(riid, ppv);
+      });
+
+  // 3. Create a dummy Native Texture backed VideoFrame whose metadata reports
+  // NV12 even though the underlying shared texture is BGRA8.
+  auto test_sii = base::MakeRefCounted<gpu::TestSharedImageInterface>();
+  gfx::GpuMemoryBufferHandle gmb_handle{gfx::DXGIHandle::CreateFakeForTest()};
+  const auto si_usage = gpu::SHARED_IMAGE_USAGE_CPU_WRITE_ONLY |
+                        gpu::SHARED_IMAGE_USAGE_DISPLAY_READ;
+
+  auto shared_image = test_sii->CreateSharedImage(
+      {viz::MultiPlaneFormat::kNV12, input_visible_size, gfx::ColorSpace(),
+       gpu::SharedImageUsageSet(si_usage),
+       "MediaFoundationVideoEncodeAcceleratorTest"},
+      gpu::kNullSurfaceHandle, gfx::BufferUsage::GPU_READ,
+      std::move(gmb_handle));
+
+  scoped_refptr<VideoFrame> frame = VideoFrame::WrapMappableSharedImage(
+      std::move(shared_image), test_sii->GenVerifiedSyncToken(),
+      base::NullCallback(), gfx::Rect(input_visible_size), input_visible_size,
+      base::TimeDelta());
+
+  VideoEncoder::EncodeOptions options(false);
+
+  // 4. Encoding the frame must reject it before issuing the copy.
+  EXPECT_CALL(*mock_d3d11_device_context_.Get(), CopySubresourceRegion)
+      .Times(0);
+  EXPECT_CALL(client_, NotifyErrorStatus(_));
+
+  // 5. Act: Attempt to encode.
+  encoder_->Encode(frame, options);
+  task_environment_.RunUntilIdle();
+}
+
 INSTANTIATE_TEST_SUITE_P(All,
                          MediaFoundationVideoEncodeAcceleratorAlignmentTest,
                          ::testing::Values(PIXEL_FORMAT_NV12,