diff --git a/src/strands/types/models/openai.py b/src/strands/types/models/openai.py
index 96f758d5..0df1dda5 100644
--- a/src/strands/types/models/openai.py
+++ b/src/strands/types/models/openai.py
@@ -57,7 +57,17 @@ def format_request_message_content(cls, content: ContentBlock) -> dict[str, Any]
 
         if "image" in content:
             mime_type = mimetypes.types_map.get(f".{content['image']['format']}", "application/octet-stream")
-            image_data = content["image"]["source"]["bytes"].decode("utf-8")
+            image_bytes = content["image"]["source"]["bytes"]
+            try:
+                base64.b64decode(image_bytes, validate=True)
+                logger.warning(
+                    "issue=<%s> | base64 encoded images will not be accepted in a future version",
+                    "https://github.com/strands-agents/sdk-python/issues/252"
+                )
+            except ValueError:
+                image_bytes = base64.b64encode(image_bytes)
+
+            image_data = image_bytes.decode("utf-8")
             return {
                 "image_url": {
                     "detail": "auto",
diff --git a/tests/strands/types/models/test_openai.py b/tests/strands/types/models/test_openai.py
index 9db08bc9..2827969d 100644
--- a/tests/strands/types/models/test_openai.py
+++ b/tests/strands/types/models/test_openai.py
@@ -1,3 +1,4 @@
+import base64
 import unittest.mock
 
 import pytest
@@ -90,7 +91,24 @@ def system_prompt():
                 "image_url": {
                     "detail": "auto",
                     "format": "image/jpeg",
-                    "url": "data:image/jpeg;base64,image",
+                    "url": "data:image/jpeg;base64,aW1hZ2U=",
+                },
+                "type": "image_url",
+            },
+        ),
+        # Image - base64 encoded
+        (
+            {
+                "image": {
+                    "format": "jpg",
+                    "source": {"bytes": base64.b64encode(b"image")},
+                },
+            },
+            {
+                "image_url": {
+                    "detail": "auto",
+                    "format": "image/jpeg",
+                    "url": "data:image/jpeg;base64,aW1hZ2U=",
                 },
                 "type": "image_url",
             },