diff --git a/swift/template/base.py b/swift/template/base.py
index 36e227b8fc..edd6944423 100644
--- a/swift/template/base.py
+++ b/swift/template/base.py
@@ -810,8 +810,12 @@ def prepare_generate_kwargs(self, generate_kwargs: Dict[str, Any], *, model=None
 
     @staticmethod
     def _save_pil_image(image: Image.Image) -> str:
+        # `Image.tobytes()` only returns the flattened pixel stream, without mode or shape.
+        # Include them in the cache key so images that share pixel bytes but differ in
+        # mode/size do not collide onto the same cached file.
         img_bytes = image.tobytes()
-        img_hash = hashlib.sha256(img_bytes).hexdigest()
+        meta = f'{image.mode}-{image.width}x{image.height}-'.encode()
+        img_hash = hashlib.sha256(meta + img_bytes).hexdigest()
         tmp_dir = os.path.join(get_cache_dir(), 'tmp', 'images')
         logger.info_once(f'create tmp_dir: {tmp_dir}')
         os.makedirs(tmp_dir, exist_ok=True)
diff --git a/tests/general/test_template.py b/tests/general/test_template.py
index da6270ae69..d853ca9b8b 100644
--- a/tests/general/test_template.py
+++ b/tests/general/test_template.py
@@ -72,8 +72,38 @@ def test_mllm_dataset_map():
     _test_dataset_map('Qwen/Qwen2-VL-7B-Instruct', 'modelscope/coco_2014_caption:validation#100')
 
 
+def test_save_pil_image_dimension_collision():
+    from PIL import Image
+
+    from swift.template.base import Template
+
+    # Two images that share the same flattened pixel bytes but differ in shape.
+    width_a, height_a = 120, 80
+    width_b, height_b = 80, 120
+    assert width_a * height_a == width_b * height_b
+    pixels = bytearray()
+    for i in range(width_a * height_a):
+        row = i // width_a
+        pixels.extend((255, 60, 60) if row % 10 < 5 else (60, 60, 255))
+    img_bytes = bytes(pixels)
+    image_a = Image.frombytes('RGB', (width_a, height_a), img_bytes)
+    image_b = Image.frombytes('RGB', (width_b, height_b), img_bytes)
+    assert image_a.tobytes() == image_b.tobytes()
+
+    path_a = Template._save_pil_image(image_a)
+    path_b = Template._save_pil_image(image_b)
+
+    # Different dimensions must not collide onto the same cache file.
+    assert path_a != path_b
+    with Image.open(path_a) as saved_a:
+        assert saved_a.size == (width_a, height_a)
+    with Image.open(path_b) as saved_b:
+        assert saved_b.size == (width_b, height_b)
+
+
 if __name__ == '__main__':
     test_template()
     test_mllm()
     test_llm_dataset_map()
     test_mllm_dataset_map()
+    test_save_pil_image_dimension_collision()