diff --git a/dev-packages/e2e-tests/test-applications/nextjs-15-basepath/app/navigation/page.tsx b/dev-packages/e2e-tests/test-applications/nextjs-15-basepath/app/navigation/page.tsx
index 918c03de3d0a..21bdce977a7f 100644
--- a/dev-packages/e2e-tests/test-applications/nextjs-15-basepath/app/navigation/page.tsx
+++ b/dev-packages/e2e-tests/test-applications/nextjs-15-basepath/app/navigation/page.tsx
@@ -17,6 +17,15 @@ export default function Page() {
           router.push()
         </button>
       </li>
+      <li>
+        <button
+          onClick={() => {
+            router.push(`${window.location.origin}/my-app/navigation/42/router-push`);
+          }}
+        >
+          Absolute URL push
+        </button>
+      </li>
       <li>
         <Link href="/navigation/42/link">Normal Link</Link>
       </li>
diff --git a/dev-packages/e2e-tests/test-applications/nextjs-15-basepath/tests/routing-basepath-span.test.ts b/dev-packages/e2e-tests/test-applications/nextjs-15-basepath/tests/routing-basepath-span.test.ts
index fbdb962d4262..c3c62b908f2c 100644
--- a/dev-packages/e2e-tests/test-applications/nextjs-15-basepath/tests/routing-basepath-span.test.ts
+++ b/dev-packages/e2e-tests/test-applications/nextjs-15-basepath/tests/routing-basepath-span.test.ts
@@ -81,3 +81,21 @@ test('Creates a navigation span for basePath <Link> with prefix', async ({ page
 
   expect(await navigationSpanPromise).toBeDefined();
 });
+
+test('Does not prepend basePath to absolute router.push URLs', async ({ page }) => {
+  const navigationSpanPromise = waitForStreamedSpan('nextjs-15-basepath', span => {
+    return getSpanOp(span) === 'navigation' && span.is_segment;
+  });
+
+  await page.goto('/my-app/navigation');
+  await page.waitForTimeout(1000);
+  await page.getByText('Absolute URL push').click();
+
+  const navigationSpan = await navigationSpanPromise;
+
+  expect(navigationSpan.name).toBe('/my-app/navigation/:param/router-push');
+  expect(navigationSpan.attributes).toMatchObject({
+    'sentry.segment.name.source': { value: 'route', type: 'string' },
+    'url.path': { value: '/my-app/navigation/42/router-push', type: 'string' },
+  });
+});
diff --git a/packages/nextjs/src/client/routing/appRouterRoutingInstrumentation.ts b/packages/nextjs/src/client/routing/appRouterRoutingInstrumentation.ts
index eb3edbf3eced..07258ff72416 100644
--- a/packages/nextjs/src/client/routing/appRouterRoutingInstrumentation.ts
+++ b/packages/nextjs/src/client/routing/appRouterRoutingInstrumentation.ts
@@ -156,7 +156,7 @@ const globalWithInjectedBasePath = GLOBAL_OBJ as typeof GLOBAL_OBJ & {
 export function appRouterInstrumentNavigation(client: Client): void {
   routerTransitionHandler = (href, navigationType) => {
     const basePath = process.env._sentryBasePath ?? globalWithInjectedBasePath._sentryBasePath;
-    const normalizedHref = basePath && !href.startsWith(basePath) ? `${basePath}${href}` : href;
+    const normalizedHref = basePath && href.startsWith('/') && !href.startsWith(basePath) ? `${basePath}${href}` : href;
     const unparameterizedPathname = stripTrailingSlash(new URL(normalizedHref, WINDOW.location.href).pathname);
     const parameterizedPathname = maybeParameterizeRoute(unparameterizedPathname);
     // With span streaming, span names have to be low cardinality, so we can't fall back to the URL.
@@ -304,7 +304,9 @@ function patchRouter(client: Client, router: NextRouter, currentNavigationSpanRe
           const href = argArray[0];
           const basePath = process.env._sentryBasePath ?? globalWithInjectedBasePath._sentryBasePath;
           const normalizedHref =
-            basePath && typeof href === 'string' && !href.startsWith(basePath) ? `${basePath}${href}` : href;
+            basePath && typeof href === 'string' && href.startsWith('/') && !href.startsWith(basePath)
+              ? `${basePath}${href}`
+              : href;
           const transactionName = stripTrailingSlash(transactionNameifyRouterArgument(normalizedHref));
           const parameterizedPathname = maybeParameterizeRoute(transactionName);
 
diff --git a/packages/nextjs/test/client/appRouterRoutingInstrumentation.test.ts b/packages/nextjs/test/client/appRouterRoutingInstrumentation.test.ts
index e54e9867cc89..37adaa05c25a 100644
--- a/packages/nextjs/test/client/appRouterRoutingInstrumentation.test.ts
+++ b/packages/nextjs/test/client/appRouterRoutingInstrumentation.test.ts
@@ -27,6 +27,7 @@ interface NextRouter {
 const globalWithNext = globalThis as typeof globalThis & {
   next?: { router?: NextRouter };
   _sentryRouteManifest?: string;
+  _sentryBasePath?: string;
 };
 
 const manifest: RouteManifest = {
@@ -38,6 +39,12 @@ const manifest: RouteManifest = {
       paramNames: ['param'],
       hasOptionalPrefix: false,
     },
+    {
+      path: '/my-app/navigation/:param/router-push',
+      regex: '^/my-app/navigation/([^/]+)/router-push$',
+      paramNames: ['param'],
+      hasOptionalPrefix: false,
+    },
   ],
   isrRoutes: [],
 };
@@ -56,6 +63,7 @@ async function setup(traceLifecycle: 'stream' | 'static'): Promise<{
   core: Core;
   router: NextRouter;
   client: Client;
+  instrumentation: Instrumentation;
 }> {
   vi.resetModules();
   const core: Core = await import('@sentry/core');
@@ -80,7 +88,7 @@ async function setup(traceLifecycle: 'stream' | 'static'): Promise<{
   instrumentation.appRouterInstrumentNavigation(client);
   await vi.waitFor(() => expect(router.back).not.toBe(originalBack));
 
-  return { core, router, client };
+  return { core, router, client, instrumentation };
 }
 
 describe('appRouterInstrumentNavigation (router-patch mode)', () => {
@@ -207,3 +215,49 @@ describe('appRouterInstrumentNavigation (router-patch mode)', () => {
     });
   });
 });
+
+describe('appRouterInstrumentNavigation with basePath', () => {
+  beforeEach(() => {
+    globalWithNext._sentryRouteManifest = JSON.stringify(manifest);
+    globalWithNext._sentryBasePath = '/my-app';
+    window.history.replaceState({}, '', '/my-app/navigation');
+  });
+
+  afterEach(() => {
+    delete globalWithNext.next;
+    delete globalWithNext._sentryRouteManifest;
+    delete globalWithNext._sentryBasePath;
+  });
+
+  it.each([
+    ['a root-relative path without basePath', '/navigation/42/router-push'],
+    ['a root-relative path with basePath', '/my-app/navigation/42/router-push'],
+    ['an absolute URL', 'http://localhost:3000/my-app/navigation/42/router-push'],
+  ])('names the router-patch navigation span correctly for %s', async (_, href) => {
+    const { core, router } = await setup('static');
+
+    router.push(href);
+
+    const span = core.getActiveSpan();
+    expect(span).toBeDefined();
+    const spanJson = core.spanToJSON(span!);
+    expect(spanJson.name).toBe('/my-app/navigation/:param/router-push');
+    expect(spanJson.attributes).toEqual(
+      expect.objectContaining({ 'url.full': 'http://localhost:3000/my-app/navigation/42/router-push' }),
+    );
+  });
+
+  it.each([
+    ['a root-relative path without basePath', '/navigation/42/router-push'],
+    ['a root-relative path with basePath', '/my-app/navigation/42/router-push'],
+    ['an absolute URL', 'http://localhost:3000/my-app/navigation/42/router-push'],
+  ])('names the transition-start-hook navigation span correctly for %s', async (_, href) => {
+    const { core, instrumentation } = await setup('static');
+
+    instrumentation.captureRouterTransitionStart(href, 'push');
+
+    const span = core.getActiveSpan();
+    expect(span).toBeDefined();
+    expect(core.spanToJSON(span!).name).toBe('/my-app/navigation/:param/router-push');
+  });
+});