diff --git a/libs/langchain-mistralai/src/chat_models.ts b/libs/langchain-mistralai/src/chat_models.ts
index 1a1fdd36e12b..4c14e304a9dd 100644
--- a/libs/langchain-mistralai/src/chat_models.ts
+++ b/libs/langchain-mistralai/src/chat_models.ts
@@ -66,6 +66,7 @@ import {
 } from "@langchain/core/runnables";
 import { zodToJsonSchema } from "zod-to-json-schema";
 import { ToolCallChunk } from "@langchain/core/messages/tool";
+import { _convertToolCallIdToMistralCompatible } from "./utils.js";
 
 interface TokenUsage {
   completionTokens?: number;
@@ -199,7 +200,10 @@ function convertMessagesToMistralMessages(
   const getTools = (message: BaseMessage): MistralAIToolCalls[] | undefined => {
     if (isAIMessage(message) && !!message.tool_calls?.length) {
       return message.tool_calls
-        .map((toolCall) => ({ ...toolCall, id: toolCall.id }))
+        .map((toolCall) => ({
+          ...toolCall,
+          id: _convertToolCallIdToMistralCompatible(toolCall.id ?? ""),
+        }))
         .map(convertLangChainToolCallToOpenAI) as MistralAIToolCalls[];
     }
     if (!message.additional_kwargs.tool_calls?.length) {
@@ -208,7 +212,7 @@ function convertMessagesToMistralMessages(
     const toolCalls: Omit<OpenAIToolCall, "index">[] =
       message.additional_kwargs.tool_calls;
     return toolCalls?.map((toolCall) => ({
-      id: toolCall.id,
+      id: _convertToolCallIdToMistralCompatible(toolCall.id),
       type: "function",
       function: toolCall.function,
     }));
@@ -217,6 +221,17 @@ function convertMessagesToMistralMessages(
   return messages.map((message) => {
     const toolCalls = getTools(message);
     const content = toolCalls === undefined ? getContent(message.content) : "";
+    if ("tool_call_id" in message && typeof message.tool_call_id === "string") {
+      return {
+        role: getRole(message._getType()),
+        content,
+        name: message.name,
+        tool_call_id: _convertToolCallIdToMistralCompatible(
+          message.tool_call_id
+        ),
+      };
+    }
+
     return {
       role: getRole(message._getType()),
       content,
diff --git a/libs/langchain-mistralai/src/tests/chat_models.standard.test.ts b/libs/langchain-mistralai/src/tests/chat_models.standard.test.ts
index c925f3dc6d47..d77997e8e258 100644
--- a/libs/langchain-mistralai/src/tests/chat_models.standard.test.ts
+++ b/libs/langchain-mistralai/src/tests/chat_models.standard.test.ts
@@ -24,7 +24,7 @@ class ChatMistralAIStandardUnitTests extends ChatModelUnitTests<
 
   expectedLsParams(): Partial<LangSmithParams> {
     console.warn(
-      "Overriding testStandardParams. ChatCloudflareWorkersAI does not support stop sequences."
+      "Overriding testStandardParams. ChatMistralAI does not support stop sequences."
     );
     return {
       ls_provider: "string",
diff --git a/libs/langchain-mistralai/src/tests/chat_models.test.ts b/libs/langchain-mistralai/src/tests/chat_models.test.ts
new file mode 100644
index 000000000000..b1dedfb0ba56
--- /dev/null
+++ b/libs/langchain-mistralai/src/tests/chat_models.test.ts
@@ -0,0 +1,29 @@
+import {
+  _isValidMistralToolCallId,
+  _convertToolCallIdToMistralCompatible,
+} from "../utils.js";
+
+describe("Mistral Tool Call ID Conversion", () => {
+  test("valid and invalid Mistral tool call IDs", () => {
+    expect(_isValidMistralToolCallId("ssAbar4Dr")).toBe(true);
+    expect(_isValidMistralToolCallId("abc123")).toBe(false);
+    expect(_isValidMistralToolCallId("call_JIIjI55tTipFFzpcP8re3BpM")).toBe(
+      false
+    );
+  });
+
+  test("tool call ID conversion", () => {
+    const resultMap: Record<string, string> = {
+      ssAbar4Dr: "ssAbar4Dr",
+      abc123: "0001yoN1K",
+      call_JIIjI55tTipFFzpcP8re3BpM: "0001sqrj5",
+      12345: "00003akVR",
+    };
+
+    for (const [inputId, expectedOutput] of Object.entries(resultMap)) {
+      const convertedId = _convertToolCallIdToMistralCompatible(inputId);
+      expect(convertedId).toBe(expectedOutput);
+      expect(_isValidMistralToolCallId(convertedId)).toBe(true);
+    }
+  });
+});
diff --git a/libs/langchain-mistralai/src/utils.ts b/libs/langchain-mistralai/src/utils.ts
new file mode 100644
index 000000000000..193efb570555
--- /dev/null
+++ b/libs/langchain-mistralai/src/utils.ts
@@ -0,0 +1,46 @@
+// Mistral enforces a specific pattern for tool call IDs
+const TOOL_CALL_ID_PATTERN = /^[a-zA-Z0-9]{9}$/;
+
+export function _isValidMistralToolCallId(toolCallId: string): boolean {
+  return TOOL_CALL_ID_PATTERN.test(toolCallId);
+}
+
+function _base62Encode(num: number): string {
+  let numCopy = num;
+  const base62 =
+    "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
+  if (numCopy === 0) return base62[0];
+  const arr: string[] = [];
+  const base = base62.length;
+  while (numCopy) {
+    arr.push(base62[numCopy % base]);
+    numCopy = Math.floor(numCopy / base);
+  }
+  return arr.reverse().join("");
+}
+
+function _simpleHash(str: string): number {
+  let hash = 0;
+  for (let i = 0; i < str.length; i += 1) {
+    const char = str.charCodeAt(i);
+    hash = (hash << 5) - hash + char;
+    hash &= hash; // Convert to 32-bit integer
+  }
+  return Math.abs(hash);
+}
+
+export function _convertToolCallIdToMistralCompatible(
+  toolCallId: string
+): string {
+  if (_isValidMistralToolCallId(toolCallId)) {
+    return toolCallId;
+  } else {
+    const hash = _simpleHash(toolCallId);
+    const base62Str = _base62Encode(hash);
+    if (base62Str.length >= 9) {
+      return base62Str.slice(0, 9);
+    } else {
+      return base62Str.padStart(9, "0");
+    }
+  }
+}