diff --git a/CHANGELOG.md b/CHANGELOG.md
index f33bd22095..9d553f5fc9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,12 @@
 > make sure you follow our [migration guide](https://docs.sentry.io/platforms/react-native/migration/) first.
 <!-- prettier-ignore-end -->
 
+## Unreleased
+
+### Features
+
+- Warn during dev builds when multiple versions of Sentry JS SDK are detected ([#6269](https://github.com/getsentry/sentry-react-native/pull/6269))
+
 ## 8.14.0
 
 ### Features
diff --git a/packages/core/src/js/sdk.tsx b/packages/core/src/js/sdk.tsx
index 84cee9a088..2ddc9121e2 100644
--- a/packages/core/src/js/sdk.tsx
+++ b/packages/core/src/js/sdk.tsx
@@ -31,6 +31,7 @@ import { DEFAULT_BUFFER_SIZE, makeNativeTransportFactory } from './transports/na
 import { getDefaultEnvironment, isExpoGo, isRunningInMetroDevServer, isWeb } from './utils/environment';
 import { getDefaultRelease } from './utils/release';
 import { safeFactory, safeTracesSampler } from './utils/safe';
+import { checkSentryJsSdkVersionMismatch } from './utils/sdkVersionCheck';
 import { RN_GLOBAL_OBJ } from './utils/worldwide';
 import { NATIVE } from './wrapper';
 
@@ -172,6 +173,9 @@ export function init(passedOptions: ReactNativeOptions): void {
     defaultIntegrations,
   });
   initAndBind(ReactNativeClient, options);
+  if (__DEV__) {
+    checkSentryJsSdkVersionMismatch();
+  }
 
   if (isExpoGo()) {
     debug.log('Offline caching, native errors features are not available in Expo Go.');
diff --git a/packages/core/src/js/utils/sdkVersionCheck.ts b/packages/core/src/js/utils/sdkVersionCheck.ts
new file mode 100644
index 0000000000..17fd5df84a
--- /dev/null
+++ b/packages/core/src/js/utils/sdkVersionCheck.ts
@@ -0,0 +1,26 @@
+import { debug, getMainCarrier, SDK_VERSION as CORE_SDK_VERSION } from '@sentry/core';
+
+export function checkSentryJsSdkVersionMismatch(): void {
+  try {
+    const carrier = getMainCarrier();
+    const sentryCarrier = carrier.__SENTRY__;
+    if (!sentryCarrier) {
+      return;
+    }
+
+    const versions = Object.keys(sentryCarrier).filter(key => key !== CORE_SDK_VERSION && key !== 'version');
+    if (versions.length === 0) {
+      return;
+    }
+
+    debug.warn(
+      `Multiple versions of Sentry JavaScript SDKs were detected in your application. ` +
+        `Found versions: ${[CORE_SDK_VERSION, ...versions].join(', ')}. ` +
+        `This may cause unexpected behavior. ` +
+        `Ensure all Sentry packages use the same version. ` +
+        `See https://docs.sentry.io/platforms/react-native/troubleshooting/ for more details.`,
+    );
+  } catch (_e) {
+    // Ignore errors from version check
+  }
+}
diff --git a/packages/core/test/utils/sdkVersionCheck.test.ts b/packages/core/test/utils/sdkVersionCheck.test.ts
new file mode 100644
index 0000000000..33b021badb
--- /dev/null
+++ b/packages/core/test/utils/sdkVersionCheck.test.ts
@@ -0,0 +1,78 @@
+const mockDebugWarn = jest.fn();
+const mockCarrier: Record<string, unknown> = {};
+
+jest.mock('@sentry/core', () => ({
+  debug: {
+    get warn() {
+      return mockDebugWarn;
+    },
+  },
+  getMainCarrier: () => mockCarrier,
+  SDK_VERSION: '10.0.0',
+}));
+
+import { checkSentryJsSdkVersionMismatch } from '../../src/js/utils/sdkVersionCheck';
+
+describe('checkSentryJsSdkVersionMismatch', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+    delete mockCarrier.__SENTRY__;
+  });
+
+  it('does not warn when only one SDK version is present', () => {
+    mockCarrier.__SENTRY__ = { '10.0.0': {} };
+
+    checkSentryJsSdkVersionMismatch();
+
+    expect(mockDebugWarn).not.toHaveBeenCalled();
+  });
+
+  it('warns when multiple SDK versions are present', () => {
+    mockCarrier.__SENTRY__ = { '10.0.0': {}, '9.0.0': {} };
+
+    checkSentryJsSdkVersionMismatch();
+
+    expect(mockDebugWarn).toHaveBeenCalledTimes(1);
+    expect(mockDebugWarn).toHaveBeenCalledWith(expect.stringContaining('Multiple versions of Sentry JavaScript SDKs'));
+    expect(mockDebugWarn).toHaveBeenCalledWith(expect.stringContaining('9.0.0'));
+    expect(mockDebugWarn).toHaveBeenCalledWith(expect.stringContaining('10.0.0'));
+  });
+
+  it('warns when more than two SDK versions are present', () => {
+    mockCarrier.__SENTRY__ = { '10.0.0': {}, '9.0.0': {}, '8.0.0': {} };
+
+    checkSentryJsSdkVersionMismatch();
+
+    expect(mockDebugWarn).toHaveBeenCalledTimes(1);
+    expect(mockDebugWarn).toHaveBeenCalledWith(expect.stringContaining('9.0.0'));
+    expect(mockDebugWarn).toHaveBeenCalledWith(expect.stringContaining('8.0.0'));
+  });
+
+  it('does not warn when carrier has the version key set by @sentry/core', () => {
+    mockCarrier.__SENTRY__ = { '10.0.0': {}, version: '10.0.0' };
+
+    checkSentryJsSdkVersionMismatch();
+
+    expect(mockDebugWarn).not.toHaveBeenCalled();
+  });
+
+  it('does not warn when __SENTRY__ is not set', () => {
+    checkSentryJsSdkVersionMismatch();
+
+    expect(mockDebugWarn).not.toHaveBeenCalled();
+  });
+
+  it('does not throw on unexpected errors', () => {
+    Object.defineProperty(mockCarrier, '__SENTRY__', {
+      get() {
+        throw new Error('test error');
+      },
+      configurable: true,
+    });
+
+    expect(() => checkSentryJsSdkVersionMismatch()).not.toThrow();
+    expect(mockDebugWarn).not.toHaveBeenCalled();
+
+    delete mockCarrier.__SENTRY__;
+  });
+});