diff --git a/.changeset/dull-nails-kneel.md b/.changeset/dull-nails-kneel.md
new file mode 100644
index 00000000000..09403953549
--- /dev/null
+++ b/.changeset/dull-nails-kneel.md
@@ -0,0 +1,5 @@
+---
+'@firebase/functions': patch
+---
+
+Allow a custom path in Firebase functions custom domain
diff --git a/packages/functions/src/service.test.ts b/packages/functions/src/service.test.ts
index 1a43b32136f..bb29f9025fe 100644
--- a/packages/functions/src/service.test.ts
+++ b/packages/functions/src/service.test.ts
@@ -70,6 +70,11 @@ describe('Firebase Functions > Service', () => {
       assert.equal(service._url('foo'), 'https://mydomain.com/foo');
     });
 
+    it('correctly sets custom domain with path', () => {
+      service = createTestService(app, 'https://mydomain.com/functions');
+      assert.equal(service._url('foo'), 'https://mydomain.com/functions/foo');
+    });
+
     it('prefers emulator to custom domain', () => {
       const service = createTestService(app, 'https://mydomain.com');
       connectFunctionsEmulator(service, 'localhost', 5005);
diff --git a/packages/functions/src/service.ts b/packages/functions/src/service.ts
index b70a5b1fe57..c5fe7fa8a85 100644
--- a/packages/functions/src/service.ts
+++ b/packages/functions/src/service.ts
@@ -122,7 +122,8 @@ export class FunctionsService implements _FirebaseService {
     // Resolve the region or custom domain overload by attempting to parse it.
     try {
       const url = new URL(regionOrCustomDomain);
-      this.customDomain = url.origin;
+      this.customDomain =
+        url.origin + (url.pathname === '/' ? '' : url.pathname);
       this.region = DEFAULT_REGION;
     } catch (e) {
       this.customDomain = null;