diff --git a/appium/webdriver/extensions/images_comparison.py b/appium/webdriver/extensions/images_comparison.py
index 6f730815..cae80168 100644
--- a/appium/webdriver/extensions/images_comparison.py
+++ b/appium/webdriver/extensions/images_comparison.py
@@ -18,9 +18,11 @@
 
 from ..mobilecommand import MobileCommand as Command
 
+Base64Payload = Union[str, bytes]
+
 
 class ImagesComparison(CanExecuteCommands):
-    def match_images_features(self, base64_image1: bytes, base64_image2: bytes, **opts: Any) -> Dict[str, Any]:
+    def match_images_features(self, base64_image1: Base64Payload, base64_image2: Base64Payload, **opts: Any) -> Dict[str, Any]:
         """Performs images matching by features.
 
         Read
@@ -66,11 +68,16 @@ def match_images_features(self, base64_image1: bytes, base64_image2: bytes, **op
             rect2 (dict): The bounding rect for the `points2` array or a zero rect if not enough matching points
                 were found. The rect is represented by a dictionary with 'x', 'y', 'width' and 'height' keys
         """
-        options = {'mode': 'matchFeatures', 'firstImage': base64_image1, 'secondImage': base64_image2, 'options': opts}
+        options = {
+            'mode': 'matchFeatures',
+            'firstImage': _adjust_image_payload(base64_image1),
+            'secondImage': _adjust_image_payload(base64_image2),
+            'options': opts,
+        }
         return self.execute(Command.COMPARE_IMAGES, options)['value']
 
     def find_image_occurrence(
-        self, base64_full_image: bytes, base64_partial_image: bytes, **opts: Any
+        self, base64_full_image: Base64Payload, base64_partial_image: Base64Payload, **opts: Any
     ) -> Dict[str, Union[bytes, Dict]]:
         """Performs images matching by template to find possible occurrence of the partial image
         in the full image.
@@ -97,13 +104,15 @@ def find_image_occurrence(
         """
         options = {
             'mode': 'matchTemplate',
-            'firstImage': base64_full_image,
-            'secondImage': base64_partial_image,
+            'firstImage': _adjust_image_payload(base64_full_image),
+            'secondImage': _adjust_image_payload(base64_partial_image),
             'options': opts,
         }
         return self.execute(Command.COMPARE_IMAGES, options)['value']
 
-    def get_images_similarity(self, base64_image1: bytes, base64_image2: bytes, **opts: Any) -> Dict[str, Union[bytes, Dict]]:
+    def get_images_similarity(
+        self, base64_image1: Base64Payload, base64_image2: Base64Payload, **opts: Any
+    ) -> Dict[str, Union[bytes, Dict]]:
         """Performs images matching to calculate the similarity score between them.
 
         The flow there is similar to the one used in
@@ -125,8 +134,17 @@ def get_images_similarity(self, base64_image1: bytes, base64_image2: bytes, **op
                 score (float): The similarity score as a float number in range [0.0, 1.0].
                     1.0 is the highest score (means both images are totally equal).
         """
-        options = {'mode': 'getSimilarity', 'firstImage': base64_image1, 'secondImage': base64_image2, 'options': opts}
+        options = {
+            'mode': 'getSimilarity',
+            'firstImage': _adjust_image_payload(base64_image1),
+            'secondImage': _adjust_image_payload(base64_image2),
+            'options': opts,
+        }
         return self.execute(Command.COMPARE_IMAGES, options)['value']
 
     def _add_commands(self) -> None:
         self.command_executor.add_command(Command.COMPARE_IMAGES, 'POST', '/session/$sessionId/appium/compare_images')
+
+
+def _adjust_image_payload(payload: Base64Payload) -> str:
+    return payload if isinstance(payload, str) else payload.decode('utf-8')