diff --git a/.changeset/fast-mangos-chew.md b/.changeset/fast-mangos-chew.md
new file mode 100644
index 00000000000..c5d2e4b4d1f
--- /dev/null
+++ b/.changeset/fast-mangos-chew.md
@@ -0,0 +1,5 @@
+---
+'@firebase/vertexai': patch
+---
+
+Pass `GenerativeModel`'s `BaseParams` to created chat sessions. This fixes an issue where `GenerationConfig` would not be inherited from `ChatSession`.
diff --git a/packages/vertexai/src/models/generative-model.test.ts b/packages/vertexai/src/models/generative-model.test.ts
index 987f9b115e2..51ea8aafead 100644
--- a/packages/vertexai/src/models/generative-model.test.ts
+++ b/packages/vertexai/src/models/generative-model.test.ts
@@ -172,7 +172,10 @@ describe('GenerativeModel', () => {
         { functionDeclarations: [{ name: 'myfunc', description: 'mydesc' }] }
       ],
       toolConfig: { functionCallingConfig: { mode: FunctionCallingMode.NONE } },
-      systemInstruction: { role: 'system', parts: [{ text: 'be friendly' }] }
+      systemInstruction: { role: 'system', parts: [{ text: 'be friendly' }] },
+      generationConfig: {
+        topK: 1
+      }
     });
     expect(genModel.tools?.length).to.equal(1);
     expect(genModel.toolConfig?.functionCallingConfig?.mode).to.equal(
@@ -196,7 +199,8 @@ describe('GenerativeModel', () => {
         return (
           value.includes('myfunc') &&
           value.includes(FunctionCallingMode.NONE) &&
-          value.includes('be friendly')
+          value.includes('be friendly') &&
+          value.includes('topK')
         );
       }),
       {}
@@ -236,7 +240,10 @@ describe('GenerativeModel', () => {
         { functionDeclarations: [{ name: 'myfunc', description: 'mydesc' }] }
       ],
       toolConfig: { functionCallingConfig: { mode: FunctionCallingMode.NONE } },
-      systemInstruction: { role: 'system', parts: [{ text: 'be friendly' }] }
+      systemInstruction: { role: 'system', parts: [{ text: 'be friendly' }] },
+      generationConfig: {
+        responseMimeType: 'image/jpeg'
+      }
     });
     expect(genModel.tools?.length).to.equal(1);
     expect(genModel.toolConfig?.functionCallingConfig?.mode).to.equal(
@@ -262,7 +269,10 @@ describe('GenerativeModel', () => {
         toolConfig: {
           functionCallingConfig: { mode: FunctionCallingMode.AUTO }
         },
-        systemInstruction: { role: 'system', parts: [{ text: 'be formal' }] }
+        systemInstruction: { role: 'system', parts: [{ text: 'be formal' }] },
+        generationConfig: {
+          responseMimeType: 'image/png'
+        }
       })
       .sendMessage('hello');
     expect(makeRequestStub).to.be.calledWith(
@@ -274,7 +284,9 @@ describe('GenerativeModel', () => {
         return (
           value.includes('otherfunc') &&
           value.includes(FunctionCallingMode.AUTO) &&
-          value.includes('be formal')
+          value.includes('be formal') &&
+          value.includes('image/png') &&
+          !value.includes('image/jpeg')
         );
       }),
       {}
diff --git a/packages/vertexai/src/models/generative-model.ts b/packages/vertexai/src/models/generative-model.ts
index 983118bf6ff..1af1ee700d5 100644
--- a/packages/vertexai/src/models/generative-model.ts
+++ b/packages/vertexai/src/models/generative-model.ts
@@ -132,6 +132,13 @@ export class GenerativeModel extends VertexAIModel {
         tools: this.tools,
         toolConfig: this.toolConfig,
         systemInstruction: this.systemInstruction,
+        generationConfig: this.generationConfig,
+        safetySettings: this.safetySettings,
+        /**
+         * Overrides params inherited from GenerativeModel with those explicitly set in the
+         * StartChatParams. For example, if startChatParams.generationConfig is set, it'll override
+         * this.generationConfig.
+         */
         ...startChatParams
       },
       this.requestOptions