diff --git a/.changeset/dirty-wolves-sin.md b/.changeset/dirty-wolves-sin.md
new file mode 100644
index 00000000..170f56df
--- /dev/null
+++ b/.changeset/dirty-wolves-sin.md
@@ -0,0 +1,5 @@
+---
+"@google/generative-ai": minor
+---
+
+Expand the model's `countTokens` method to alternatively accept a `GenerateContentRequest`.
diff --git a/docs/reference/main/generative-ai.counttokensrequest.contents.md b/docs/reference/main/generative-ai.counttokensrequest.contents.md
index 693fe3d5..948e6c79 100644
--- a/docs/reference/main/generative-ai.counttokensrequest.contents.md
+++ b/docs/reference/main/generative-ai.counttokensrequest.contents.md
@@ -7,5 +7,5 @@
 **Signature:**
 
 ```typescript
-contents: Content[];
+contents?: Content[];
 ```
diff --git a/docs/reference/main/generative-ai.counttokensrequest.generatecontentrequest.md b/docs/reference/main/generative-ai.counttokensrequest.generatecontentrequest.md
new file mode 100644
index 00000000..86bf60ad
--- /dev/null
+++ b/docs/reference/main/generative-ai.counttokensrequest.generatecontentrequest.md
@@ -0,0 +1,11 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [@google/generative-ai](./generative-ai.md) &gt; [CountTokensRequest](./generative-ai.counttokensrequest.md) &gt; [generateContentRequest](./generative-ai.counttokensrequest.generatecontentrequest.md)
+
+## CountTokensRequest.generateContentRequest property
+
+**Signature:**
+
+```typescript
+generateContentRequest?: GenerateContentRequest;
+```
diff --git a/docs/reference/main/generative-ai.counttokensrequest.md b/docs/reference/main/generative-ai.counttokensrequest.md
index 7895bfcc..5217e1b3 100644
--- a/docs/reference/main/generative-ai.counttokensrequest.md
+++ b/docs/reference/main/generative-ai.counttokensrequest.md
@@ -4,7 +4,9 @@
 
 ## CountTokensRequest interface
 
-Params for calling [GenerativeModel.countTokens()](./generative-ai.generativemodel.counttokens.md)
+Params for calling [GenerativeModel.countTokens()](./generative-ai.generativemodel.counttokens.md)<!-- -->.
+
+The request must contain either a [Content](./generative-ai.content.md) array or a [GenerateContentRequest](./generative-ai.generatecontentrequest.md)<!-- -->, but not both. If both are provided then a [GoogleGenerativeAIRequestInputError](./generative-ai.googlegenerativeairequestinputerror.md) is thrown.
 
 **Signature:**
 
@@ -16,5 +18,6 @@ export interface CountTokensRequest
 
 |  Property | Modifiers | Type | Description |
 |  --- | --- | --- | --- |
-|  [contents](./generative-ai.counttokensrequest.contents.md) |  | [Content](./generative-ai.content.md)<!-- -->\[\] |  |
+|  [contents?](./generative-ai.counttokensrequest.contents.md) |  | [Content](./generative-ai.content.md)<!-- -->\[\] | _(Optional)_ |
+|  [generateContentRequest?](./generative-ai.counttokensrequest.generatecontentrequest.md) |  | [GenerateContentRequest](./generative-ai.generatecontentrequest.md) | _(Optional)_ |
 
diff --git a/docs/reference/main/generative-ai.md b/docs/reference/main/generative-ai.md
index ec5a3a7c..e2719d97 100644
--- a/docs/reference/main/generative-ai.md
+++ b/docs/reference/main/generative-ai.md
@@ -40,7 +40,7 @@
 |  [CitationSource](./generative-ai.citationsource.md) | A single citation source. |
 |  [Content](./generative-ai.content.md) | Content type for both prompts and response candidates. |
 |  [ContentEmbedding](./generative-ai.contentembedding.md) | A single content embedding. |
-|  [CountTokensRequest](./generative-ai.counttokensrequest.md) | Params for calling [GenerativeModel.countTokens()](./generative-ai.generativemodel.counttokens.md) |
+|  [CountTokensRequest](./generative-ai.counttokensrequest.md) | <p>Params for calling [GenerativeModel.countTokens()](./generative-ai.generativemodel.counttokens.md)<!-- -->.</p><p>The request must contain either a [Content](./generative-ai.content.md) array or a [GenerateContentRequest](./generative-ai.generatecontentrequest.md)<!-- -->, but not both. If both are provided then a [GoogleGenerativeAIRequestInputError](./generative-ai.googlegenerativeairequestinputerror.md) is thrown.</p> |
 |  [CountTokensResponse](./generative-ai.counttokensresponse.md) | Response from calling [GenerativeModel.countTokens()](./generative-ai.generativemodel.counttokens.md)<!-- -->. |
 |  [EmbedContentRequest](./generative-ai.embedcontentrequest.md) | Params for calling [GenerativeModel.embedContent()](./generative-ai.generativemodel.embedcontent.md) |
 |  [EmbedContentResponse](./generative-ai.embedcontentresponse.md) | Response from calling [GenerativeModel.embedContent()](./generative-ai.generativemodel.embedcontent.md)<!-- -->. |
diff --git a/packages/main/src/models/generative-model.test.ts b/packages/main/src/models/generative-model.test.ts
index 5f4ce1c9..f61a1375 100644
--- a/packages/main/src/models/generative-model.test.ts
+++ b/packages/main/src/models/generative-model.test.ts
@@ -18,6 +18,7 @@ import { expect, use } from "chai";
 import { GenerativeModel } from "./generative-model";
 import * as sinonChai from "sinon-chai";
 import {
+  CountTokensRequest,
   FunctionCallingMode,
   HarmBlockThreshold,
   HarmCategory,
@@ -319,4 +320,34 @@ describe("GenerativeModel", () => {
     );
     restore();
   });
+  it("countTokens errors if contents and generateContentRequest are both defined", async () => {
+    const genModel = new GenerativeModel(
+      "apiKey",
+      {
+        model: "my-model",
+      },
+      {
+        apiVersion: "v2000",
+      },
+    );
+    const mockResponse = getMockResponse(
+      "unary-success-basic-reply-short.json",
+    );
+    const makeRequestStub = stub(request, "makeRequest").resolves(
+      mockResponse as Response,
+    );
+    const countTokensRequest: CountTokensRequest = {
+      contents: [{ role: "user", parts: [{ text: "hello" }] }],
+      generateContentRequest: {
+        contents: [{ role: "user", parts: [{ text: "hello" }] }],
+      },
+    };
+    await expect(
+      genModel.countTokens(countTokensRequest),
+    ).to.eventually.be.rejectedWith(
+      "CountTokensRequest must have one of contents or generateContentRequest, not both.",
+    );
+    expect(makeRequestStub).to.not.be.called;
+    restore();
+  });
 });
diff --git a/packages/main/src/models/generative-model.ts b/packages/main/src/models/generative-model.ts
index df1ecfa9..4bc2c63e 100644
--- a/packages/main/src/models/generative-model.ts
+++ b/packages/main/src/models/generative-model.ts
@@ -43,6 +43,7 @@ import { ChatSession } from "../methods/chat-session";
 import { countTokens } from "../methods/count-tokens";
 import { batchEmbedContents, embedContent } from "../methods/embed-content";
 import {
+  formatCountTokensInput,
   formatEmbedContentInput,
   formatGenerateContentInput,
   formatSystemInstruction,
@@ -157,7 +158,7 @@ export class GenerativeModel {
   async countTokens(
     request: CountTokensRequest | string | Array<string | Part>,
   ): Promise<CountTokensResponse> {
-    const formattedParams = formatGenerateContentInput(request);
+    const formattedParams = formatCountTokensInput(request, this.model);
     return countTokens(
       this.apiKey,
       this.model,
diff --git a/packages/main/src/requests/request-helpers.ts b/packages/main/src/requests/request-helpers.ts
index 9c6694a8..afadaefc 100644
--- a/packages/main/src/requests/request-helpers.ts
+++ b/packages/main/src/requests/request-helpers.ts
@@ -17,11 +17,16 @@
 
 import {
   Content,
+  CountTokensRequest,
+  CountTokensRequestInternal,
   EmbedContentRequest,
   GenerateContentRequest,
   Part,
 } from "../../types";
-import { GoogleGenerativeAIError } from "../errors";
+import {
+  GoogleGenerativeAIError,
+  GoogleGenerativeAIRequestInputError,
+} from "../errors";
 
 export function formatSystemInstruction(
   input?: string | Part | Content,
@@ -104,6 +109,31 @@ function assignRoleToPartsAndValidateSendMessageRequest(
   return functionContent;
 }
 
+export function formatCountTokensInput(
+  params: CountTokensRequest | string | Array<string | Part>,
+  model: string,
+): CountTokensRequestInternal {
+  let formattedRequest: CountTokensRequestInternal = {};
+  const containsGenerateContentRequest =
+    (params as CountTokensRequest).generateContentRequest != null;
+  if ((params as CountTokensRequest).contents) {
+    if (containsGenerateContentRequest) {
+      throw new GoogleGenerativeAIRequestInputError(
+        "CountTokensRequest must have one of contents or generateContentRequest, not both.",
+      );
+    }
+    formattedRequest = { ...(params as CountTokensRequest) };
+  } else if (containsGenerateContentRequest) {
+    formattedRequest = { ...(params as CountTokensRequest) };
+    formattedRequest.generateContentRequest.model = model;
+  } else {
+    // Array or string
+    const content = formatNewContent(params as string | Array<string | Part>);
+    formattedRequest.contents = [content];
+  }
+  return formattedRequest;
+}
+
 export function formatGenerateContentInput(
   params: GenerateContentRequest | string | Array<string | Part>,
 ): GenerateContentRequest {
diff --git a/packages/main/test-integration/node/count-tokens.test.ts b/packages/main/test-integration/node/count-tokens.test.ts
index 7e8dda45..76288198 100644
--- a/packages/main/test-integration/node/count-tokens.test.ts
+++ b/packages/main/test-integration/node/count-tokens.test.ts
@@ -18,6 +18,7 @@
 import { expect, use } from "chai";
 import * as chaiAsPromised from "chai-as-promised";
 import { GoogleGenerativeAI, HarmBlockThreshold, HarmCategory } from "../..";
+import { CountTokensRequest } from "../../types";
 
 use(chaiAsPromised);
 
@@ -46,4 +47,23 @@ describe("countTokens", function () {
     expect(response1.totalTokens).to.equal(3);
     expect(response2.totalTokens).to.equal(3);
   });
+  it("counts tokens with GenerateContentRequest", async () => {
+    const genAI = new GoogleGenerativeAI(process.env.GEMINI_API_KEY || "");
+    const model = genAI.getGenerativeModel({
+      model: "gemini-1.5-flash-latest",
+      safetySettings: [
+        {
+          category: HarmCategory.HARM_CATEGORY_HARASSMENT,
+          threshold: HarmBlockThreshold.BLOCK_ONLY_HIGH,
+        },
+      ],
+    });
+    const countTokensRequest: CountTokensRequest = {
+      generateContentRequest: {
+        contents: [{ role: "user", parts: [{ text: "count me" }] }],
+      },
+    };
+    const response = await model.countTokens(countTokensRequest);
+    expect(response.totalTokens).to.equal(3);
+  });
 });
diff --git a/packages/main/types/requests.ts b/packages/main/types/requests.ts
index 6787ea8b..9152f489 100644
--- a/packages/main/types/requests.ts
+++ b/packages/main/types/requests.ts
@@ -54,6 +54,14 @@ export interface GenerateContentRequest extends BaseParams {
   systemInstruction?: string | Part | Content;
 }
 
+/**
+ * Request sent to `generateContent` endpoint.
+ * @internal
+ */
+export interface GenerateContentRequestInternal extends GenerateContentRequest {
+  model?: string;
+}
+
 /**
  * Safety setting that can be sent as part of request parameters.
  * @public
@@ -95,11 +103,26 @@ export interface StartChatParams extends BaseParams {
 }
 
 /**
- * Params for calling {@link GenerativeModel.countTokens}
+ * Params for calling {@link GenerativeModel.countTokens}.
+ *
+ * The request must contain either a {@link Content} array or a
+ * {@link GenerateContentRequest}, but not both. If both are provided
+ * then a {@link GoogleGenerativeAIRequestInputError} is thrown.
+ *
  * @public
  */
 export interface CountTokensRequest {
-  contents: Content[];
+  generateContentRequest?: GenerateContentRequest;
+  contents?: Content[];
+}
+
+/**
+ * Params for calling {@link GenerativeModel.countTokens}
+ * @internal
+ */
+export interface CountTokensRequestInternal {
+  generateContentRequest?: GenerateContentRequestInternal;
+  contents?: Content[];
 }
 
 /**