diff --git a/packages/browser/src/integrations/featureFlags/growthbook/types.ts b/packages/browser/src/integrations/featureFlags/growthbook/types.ts
index 5a852d633da9..94d5a8ab2294 100644
--- a/packages/browser/src/integrations/featureFlags/growthbook/types.ts
+++ b/packages/browser/src/integrations/featureFlags/growthbook/types.ts
@@ -3,5 +3,5 @@ export interface GrowthBook {
   getFeatureValue(this: GrowthBook, featureKey: string, defaultValue: unknown, ...rest: unknown[]): unknown;
 }
 
-// We only depend on the surface we wrap; constructor args are irrelevant here.
-export type GrowthBookClass = new (...args: unknown[]) => GrowthBook;
+// We only depend on the surface we wrap, so accept any class whose prototype matches.
+export type GrowthBookClass = { prototype: GrowthBook };
diff --git a/packages/browser/test/integrations/featureFlags/growthbook/integration.test.ts b/packages/browser/test/integrations/featureFlags/growthbook/integration.test.ts
new file mode 100644
index 000000000000..b689d0a436a8
--- /dev/null
+++ b/packages/browser/test/integrations/featureFlags/growthbook/integration.test.ts
@@ -0,0 +1,37 @@
+import { getCurrentScope } from '@sentry/core/browser';
+import { afterEach, describe, expect, it } from 'vitest';
+import { growthbookIntegration } from '../../../../src/integrations/featureFlags/growthbook';
+
+describe('growthbookIntegration', () => {
+  afterEach(() => {
+    getCurrentScope().clear();
+  });
+
+  it('accepts a precisely-typed GrowthBook class without a cast and captures boolean evaluations', () => {
+    class MockGrowthBook {
+      public constructor(_options?: { apiHost: string }) {}
+
+      public isOn(_key: string): boolean {
+        return true;
+      }
+
+      public getFeatureValue(_key: string, _defaultValue: unknown): unknown {
+        return false;
+      }
+    }
+
+    const integration = growthbookIntegration({
+      growthbookClass: MockGrowthBook,
+    });
+    integration.setupOnce?.();
+
+    const growthbook = new MockGrowthBook();
+    growthbook.isOn('my-feature');
+    growthbook.getFeatureValue('my-other-feature', true);
+
+    expect(getCurrentScope().getScopeData().contexts.flags?.values).toEqual([
+      { flag: 'my-feature', result: true },
+      { flag: 'my-other-feature', result: false },
+    ]);
+  });
+});
diff --git a/packages/core/src/integrations/featureFlags/growthbook.ts b/packages/core/src/integrations/featureFlags/growthbook.ts
index 6f3d4bfe73fd..6193e271e9cc 100644
--- a/packages/core/src/integrations/featureFlags/growthbook.ts
+++ b/packages/core/src/integrations/featureFlags/growthbook.ts
@@ -14,7 +14,7 @@ interface GrowthBookLike {
   getFeatureValue(this: GrowthBookLike, featureKey: string, defaultValue: unknown, ...rest: unknown[]): unknown;
 }
 
-export type GrowthBookClassLike = new (...args: unknown[]) => GrowthBookLike;
+export type GrowthBookClassLike = { prototype: GrowthBookLike };
 
 /**
  * Sentry integration for capturing feature flag evaluations from GrowthBook.
@@ -40,7 +40,7 @@ export const growthbookIntegration: IntegrationFn = defineIntegration(
       name: 'GrowthBook' as const,
 
       setupOnce() {
-        const proto = growthbookClass.prototype as GrowthBookLike;
+        const proto = growthbookClass.prototype;
 
         // Type guard and wrap isOn
         if (typeof proto.isOn === 'function') {