diff --git a/libs/partners/anthropic/langchain_anthropic/chat_models.py b/libs/partners/anthropic/langchain_anthropic/chat_models.py
index 4a216d2c18..7d0dce4956 100644
--- a/libs/partners/anthropic/langchain_anthropic/chat_models.py
+++ b/libs/partners/anthropic/langchain_anthropic/chat_models.py
@@ -10,6 +10,7 @@ from typing import (
     Dict,
     Iterator,
     List,
+    Literal,
     Mapping,
     Optional,
     Sequence,
@@ -38,6 +39,7 @@ from langchain_core.messages import (
     BaseMessage,
     HumanMessage,
     SystemMessage,
+    ToolCall,
     ToolMessage,
 )
 from langchain_core.outputs import ChatGeneration, ChatGenerationChunk, ChatResult
@@ -156,7 +158,7 @@ def _format_messages(messages: List[BaseMessage]) -> Tuple[Optional[str], List[D
             continue
 
         role = _message_type_lookups[message.type]
-        content: Union[str, List[Dict]]
+        content: Union[str, List]
 
         if not isinstance(message.content, str):
             # parse as dict
@@ -195,6 +197,20 @@ def _format_messages(messages: List[BaseMessage]) -> Tuple[Optional[str], List[D
                     raise ValueError(
                         f"Content items must be str or dict, instead was: {type(item)}"
                     )
+        elif (
+            isinstance(message, AIMessage)
+            and not isinstance(message.content, list)
+            and message.tool_calls
+        ):
+            content = (
+                []
+                if not message.content
+                else [{"type": "text", "text": message.content}]
+            )
+            # Note: Anthropic can't have invalid tool calls as presently defined,
+            # since the model already returns dicts args not JSON strings, and invalid
+            # tool calls are those with invalid JSON for args.
+            content += _lc_tool_calls_to_anthropic_tool_use_blocks(message.tool_calls)
         else:
             content = message.content
 
@@ -677,6 +693,29 @@ def _tools_in_params(params: dict) -> bool:
     )
 
 
+class _AnthropicToolUse(TypedDict):
+    type: Literal["tool_use"]
+    name: str
+    input: dict
+    id: str
+
+
+def _lc_tool_calls_to_anthropic_tool_use_blocks(
+    tool_calls: List[ToolCall],
+) -> List[_AnthropicToolUse]:
+    blocks = []
+    for tool_call in tool_calls:
+        blocks.append(
+            _AnthropicToolUse(
+                type="tool_use",
+                name=tool_call["name"],
+                input=tool_call["args"],
+                id=cast(str, tool_call["id"]),
+            )
+        )
+    return blocks
+
+
 @deprecated(since="0.1.0", removal="0.2.0", alternative="ChatAnthropic")
 class ChatAnthropicMessages(ChatAnthropic):
     pass
diff --git a/libs/partners/anthropic/pyproject.toml b/libs/partners/anthropic/pyproject.toml
index e7320a9075..5d83e0fb67 100644
--- a/libs/partners/anthropic/pyproject.toml
+++ b/libs/partners/anthropic/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "langchain-anthropic"
-version = "0.1.8"
+version = "0.1.9"
 description = "An integration package connecting AnthropicMessages and LangChain"
 authors = []
 readme = "README.md"
diff --git a/libs/partners/anthropic/tests/unit_tests/test_chat_models.py b/libs/partners/anthropic/tests/unit_tests/test_chat_models.py
index 85019553fe..9373b0a1ea 100644
--- a/libs/partners/anthropic/tests/unit_tests/test_chat_models.py
+++ b/libs/partners/anthropic/tests/unit_tests/test_chat_models.py
@@ -11,7 +11,11 @@ from langchain_core.pydantic_v1 import BaseModel, Field, SecretStr
 from langchain_core.tools import BaseTool
 
 from langchain_anthropic import ChatAnthropic
-from langchain_anthropic.chat_models import _merge_messages, convert_to_anthropic_tool
+from langchain_anthropic.chat_models import (
+    _format_messages,
+    _merge_messages,
+    convert_to_anthropic_tool,
+)
 
 os.environ["ANTHROPIC_API_KEY"] = "foo"
 
@@ -268,3 +272,131 @@ def test_convert_to_anthropic_tool(
     for fn in (pydantic, function, dummy_tool, json_schema, expected, openai_function):
         actual = convert_to_anthropic_tool(fn)  # type: ignore
         assert actual == expected
+
+
+def test__format_messages_with_tool_calls() -> None:
+    system = SystemMessage("fuzz")
+    human = HumanMessage("foo")
+    ai = AIMessage(
+        "",
+        tool_calls=[{"name": "bar", "id": "1", "args": {"baz": "buzz"}}],
+    )
+    tool = ToolMessage(
+        "blurb",
+        tool_call_id="1",
+    )
+    messages = [system, human, ai, tool]
+    expected = (
+        "fuzz",
+        [
+            {"role": "user", "content": "foo"},
+            {
+                "role": "assistant",
+                "content": [
+                    {
+                        "type": "tool_use",
+                        "name": "bar",
+                        "id": "1",
+                        "input": {"baz": "buzz"},
+                    }
+                ],
+            },
+            {
+                "role": "user",
+                "content": [
+                    {"type": "tool_result", "content": "blurb", "tool_use_id": "1"}
+                ],
+            },
+        ],
+    )
+    actual = _format_messages(messages)
+    assert expected == actual
+
+
+def test__format_messages_with_str_content_and_tool_calls() -> None:
+    system = SystemMessage("fuzz")
+    human = HumanMessage("foo")
+    # If content and tool_calls are specified and content is a string, then both are
+    # included with content first.
+    ai = AIMessage(
+        "thought",
+        tool_calls=[{"name": "bar", "id": "1", "args": {"baz": "buzz"}}],
+    )
+    tool = ToolMessage(
+        "blurb",
+        tool_call_id="1",
+    )
+    messages = [system, human, ai, tool]
+    expected = (
+        "fuzz",
+        [
+            {"role": "user", "content": "foo"},
+            {
+                "role": "assistant",
+                "content": [
+                    {
+                        "type": "text",
+                        "text": "thought",
+                    },
+                    {
+                        "type": "tool_use",
+                        "name": "bar",
+                        "id": "1",
+                        "input": {"baz": "buzz"},
+                    },
+                ],
+            },
+            {
+                "role": "user",
+                "content": [
+                    {"type": "tool_result", "content": "blurb", "tool_use_id": "1"}
+                ],
+            },
+        ],
+    )
+    actual = _format_messages(messages)
+    assert expected == actual
+
+
+def test__format_messages_with_list_content_and_tool_calls() -> None:
+    system = SystemMessage("fuzz")
+    human = HumanMessage("foo")
+    # If content and tool_calls are specified and content is a list, then content is
+    # preferred.
+    ai = AIMessage(
+        [
+            {
+                "type": "text",
+                "text": "thought",
+            }
+        ],
+        tool_calls=[{"name": "bar", "id": "1", "args": {"baz": "buzz"}}],
+    )
+    tool = ToolMessage(
+        "blurb",
+        tool_call_id="1",
+    )
+    messages = [system, human, ai, tool]
+    expected = (
+        "fuzz",
+        [
+            {"role": "user", "content": "foo"},
+            {
+                "role": "assistant",
+                "content": [
+                    {
+                        "type": "text",
+                        "text": "thought",
+                    }
+                ],
+            },
+            {
+                "role": "user",
+                "content": [
+                    {"type": "tool_result", "content": "blurb", "tool_use_id": "1"}
+                ],
+            },
+        ],
+    )
+    actual = _format_messages(messages)
+    assert expected == actual