diff --git a/pydantic_ai_slim/pydantic_ai/models/anthropic.py b/pydantic_ai_slim/pydantic_ai/models/anthropic.py
index 1bfd918f..edf19402 100644
--- a/pydantic_ai_slim/pydantic_ai/models/anthropic.py
+++ b/pydantic_ai_slim/pydantic_ai/models/anthropic.py
@@ -130,15 +130,14 @@ def __init__(
                 client to use, if provided, `api_key` and `http_client` must be `None`.
             http_client: An existing `httpx.AsyncClient` to use for making HTTP requests.
         """
+        self._http_client = http_client or cached_async_http_client()
         self._model_name = model_name
         if anthropic_client is not None:
             assert http_client is None, 'Cannot provide both `anthropic_client` and `http_client`'
             assert api_key is None, 'Cannot provide both `anthropic_client` and `api_key`'
             self.client = anthropic_client
-        elif http_client is not None:
-            self.client = AsyncAnthropic(api_key=api_key, http_client=http_client)
         else:
-            self.client = AsyncAnthropic(api_key=api_key, http_client=cached_async_http_client())
+            self.client = AsyncAnthropic(api_key=api_key, http_client=self._http_client)
 
     async def request(
         self,
@@ -218,7 +217,7 @@ async def _messages_create(
             if (allow_parallel_tool_calls := model_settings.get('parallel_tool_calls')) is not None:
                 tool_choice['disable_parallel_tool_use'] = not allow_parallel_tool_calls
 
-        system_prompt, anthropic_messages = self._map_message(messages)
+        system_prompt, anthropic_messages = await self._map_message(messages)
 
         return await self.client.messages.create(
             max_tokens=model_settings.get('max_tokens', 1024),
@@ -270,7 +269,7 @@ def _get_tools(self, model_request_parameters: ModelRequestParameters) -> list[T
             tools += [self._map_tool_definition(r) for r in model_request_parameters.result_tools]
         return tools
 
-    def _map_message(self, messages: list[ModelMessage]) -> tuple[str, list[MessageParam]]:
+    async def _map_message(self, messages: list[ModelMessage]) -> tuple[str, list[MessageParam]]:
         """Just maps a `pydantic_ai.Message` to a `anthropic.types.MessageParam`."""
         system_prompt: str = ''
         anthropic_messages: list[MessageParam] = []
@@ -280,7 +279,7 @@ def _map_message(self, messages: list[ModelMessage]) -> tuple[str, list[MessageP
                     if isinstance(part, SystemPromptPart):
                         system_prompt += part.content
                     elif isinstance(part, UserPromptPart):
-                        anthropic_messages.append(_map_user_prompt(part))
+                        anthropic_messages.append(await _map_user_prompt(part, self._http_client))
                     elif isinstance(part, ToolReturnPart):
                         anthropic_messages.append(
                             MessageParam(
@@ -372,7 +371,7 @@ def _map_usage(message: AnthropicMessage | RawMessageStreamEvent) -> usage.Usage
     )
 
 
-def _map_user_prompt(part: UserPromptPart) -> MessageParam:
+async def _map_user_prompt(part: UserPromptPart, http_client: AsyncHTTPClient) -> MessageParam:
     part_content: str | list[ImageBlockParam | TextBlockParam]
     if isinstance(part.content, str):
         part_content = part.content
@@ -395,7 +394,19 @@ def _map_user_prompt(part: UserPromptPart) -> MessageParam:
                 )
                 part_content.append(image_block)
             elif isinstance(item, ImageUrl):
-                raise ValueError('ImageUrl is not supported in Anthropic')
+                response = await http_client.get(item.url)
+                response.raise_for_status()
+                image_block = ImageBlockParam(
+                    source={
+                        'data': io.BytesIO(response.content),
+                        'media_type': 'image/jpeg',
+                        'type': 'base64',
+                    },
+                    type='image',
+                )
+                part_content.append(image_block)
+            else:
+                raise ValueError(f'Unsupported content type: {type(item)}')
     return MessageParam(role='user', content=part_content)