diff --git a/packages/puppeteer-core/src/common/bidi/Browser.ts b/packages/puppeteer-core/src/common/bidi/Browser.ts
index f0282a751b4..9741ce7129d 100644
--- a/packages/puppeteer-core/src/common/bidi/Browser.ts
+++ b/packages/puppeteer-core/src/common/bidi/Browser.ts
@@ -24,6 +24,7 @@ import {
   BrowserContextOptions,
 } from '../../api/Browser.js';
 import {BrowserContext as BrowserContextBase} from '../../api/BrowserContext.js';
+import {Viewport} from '../PuppeteerViewport.js';
 
 import {BrowserContext} from './BrowserContext.js';
 import {Connection} from './Connection.js';
@@ -48,12 +49,14 @@ export class Browser extends BrowserBase {
   #process?: ChildProcess;
   #closeCallback?: BrowserCloseCallback;
   #connection: Connection;
+  #defaultViewport: Viewport | null;
 
   constructor(opts: Options) {
     super();
     this.#process = opts.process;
     this.#closeCallback = opts.closeCallback;
     this.#connection = opts.connection;
+    this.#defaultViewport = opts.defaultViewport;
   }
 
   override async close(): Promise<void> {
@@ -72,7 +75,9 @@ export class Browser extends BrowserBase {
   override async createIncognitoBrowserContext(
     _options?: BrowserContextOptions
   ): Promise<BrowserContextBase> {
-    return new BrowserContext(this.#connection);
+    return new BrowserContext(this.#connection, {
+      defaultViewport: this.#defaultViewport,
+    });
   }
 }
 
@@ -80,4 +85,5 @@ interface Options {
   process?: ChildProcess;
   closeCallback?: BrowserCloseCallback;
   connection: Connection;
+  defaultViewport: Viewport | null;
 }
diff --git a/packages/puppeteer-core/src/common/bidi/BrowserContext.ts b/packages/puppeteer-core/src/common/bidi/BrowserContext.ts
index e015586ee39..92950b87b02 100644
--- a/packages/puppeteer-core/src/common/bidi/BrowserContext.ts
+++ b/packages/puppeteer-core/src/common/bidi/BrowserContext.ts
@@ -16,20 +16,27 @@
 
 import {BrowserContext as BrowserContextBase} from '../../api/BrowserContext.js';
 import {Page as PageBase} from '../../api/Page.js';
+import {Viewport} from '../PuppeteerViewport.js';
 
 import {Connection} from './Connection.js';
 import {Context} from './Context.js';
 import {Page} from './Page.js';
 
+interface BrowserContextOptions {
+  defaultViewport: Viewport | null;
+}
+
 /**
  * @internal
  */
 export class BrowserContext extends BrowserContextBase {
   #connection: Connection;
+  #defaultViewport: Viewport | null;
 
-  constructor(connection: Connection) {
+  constructor(connection: Connection, options: BrowserContextOptions) {
     super();
     this.#connection = connection;
+    this.#defaultViewport = options.defaultViewport;
   }
 
   override async newPage(): Promise<PageBase> {
@@ -37,7 +44,15 @@ export class BrowserContext extends BrowserContextBase {
       type: 'tab',
     });
     const context = this.#connection.context(result.context) as Context;
-    return new Page(context);
+    const page = new Page(context);
+    if (this.#defaultViewport) {
+      try {
+        await page.setViewport(this.#defaultViewport);
+      } catch {
+        // No support for setViewport in Firefox.
+      }
+    }
+    return page;
   }
 
   override async close(): Promise<void> {}
diff --git a/packages/puppeteer-core/src/node/ProductLauncher.ts b/packages/puppeteer-core/src/node/ProductLauncher.ts
index 3c3b7b790ac..719051930f6 100644
--- a/packages/puppeteer-core/src/node/ProductLauncher.ts
+++ b/packages/puppeteer-core/src/node/ProductLauncher.ts
@@ -30,6 +30,7 @@ import {Connection} from '../common/Connection.js';
 import {TimeoutError} from '../common/Errors.js';
 import {NodeWebSocketTransport as WebSocketTransport} from '../common/NodeWebSocketTransport.js';
 import {Product} from '../common/Product.js';
+import {Viewport} from '../common/PuppeteerViewport.js';
 import {debugError} from '../common/util.js';
 
 import {
@@ -139,6 +140,7 @@ export class ProductLauncher {
             timeout,
             protocolTimeout,
             slowMo,
+            defaultViewport,
           }
         );
       } else {
@@ -159,7 +161,13 @@ export class ProductLauncher {
           browser = await this.createBiDiOverCDPBrowser(
             browserProcess,
             connection,
-            browserCloseCallback
+            browserCloseCallback,
+            {
+              timeout,
+              protocolTimeout,
+              slowMo,
+              defaultViewport,
+            }
           );
         } else {
           browser = await CDPBrowser._create(
@@ -313,8 +321,15 @@ export class ProductLauncher {
   protected async createBiDiOverCDPBrowser(
     browserProcess: ReturnType<typeof launch>,
     connection: Connection,
-    closeCallback: BrowserCloseCallback
+    closeCallback: BrowserCloseCallback,
+    opts: {
+      timeout: number;
+      protocolTimeout: number | undefined;
+      slowMo: number;
+      defaultViewport: Viewport | null;
+    }
   ): Promise<Browser> {
+    // TODO: use other options too.
     const BiDi = await import(
       /* webpackIgnore: true */ '../common/bidi/bidi.js'
     );
@@ -323,6 +338,7 @@ export class ProductLauncher {
       connection: bidiConnection,
       closeCallback,
       process: browserProcess.nodeProcess,
+      defaultViewport: opts.defaultViewport,
     });
   }
 
@@ -332,7 +348,12 @@ export class ProductLauncher {
   protected async createBiDiBrowser(
     browserProcess: ReturnType<typeof launch>,
     closeCallback: BrowserCloseCallback,
-    opts: {timeout: number; protocolTimeout: number | undefined; slowMo: number}
+    opts: {
+      timeout: number;
+      protocolTimeout: number | undefined;
+      slowMo: number;
+      defaultViewport: Viewport | null;
+    }
   ): Promise<Browser> {
     const browserWSEndpoint =
       (await browserProcess.waitForLineOutput(
@@ -348,10 +369,12 @@ export class ProductLauncher {
       opts.slowMo,
       opts.protocolTimeout
     );
+    // TODO: use other options too.
     return await BiDi.Browser.create({
       connection: bidiConnection,
       closeCallback,
       process: browserProcess.nodeProcess,
+      defaultViewport: opts.defaultViewport,
     });
   }
 
diff --git a/test/TestExpectations.json b/test/TestExpectations.json
index fc532f48929..e305f5a2330 100644
--- a/test/TestExpectations.json
+++ b/test/TestExpectations.json
@@ -725,6 +725,12 @@
     "parameters": ["cdp", "firefox"],
     "expectations": ["PASS", "TIMEOUT"]
   },
+  {
+    "testIdPattern": "[emulation.spec] Emulation Page.viewport should get the proper viewport size",
+    "platforms": ["darwin", "linux", "win32"],
+    "parameters": ["chrome", "webDriverBiDi"],
+    "expectations": ["PASS"]
+  },
   {
     "testIdPattern": "[emulation.spec] Emulation Page.viewport should support landscape emulation",
     "platforms": ["darwin", "linux", "win32"],