diff --git a/packages/auth/src/api/account_management/email_and_password.test.ts b/packages/auth/src/api/account_management/email_and_password.test.ts
index e5268860b47..44af356cfd3 100644
--- a/packages/auth/src/api/account_management/email_and_password.test.ts
+++ b/packages/auth/src/api/account_management/email_and_password.test.ts
@@ -27,6 +27,7 @@ import * as mockFetch from '../../../test/helpers/mock_fetch';
 import { ServerError } from '../errors';
 import {
   applyActionCode,
+  linkEmailPassword,
   resetPassword,
   updateEmailPassword
 } from './email_and_password';
@@ -91,6 +92,65 @@ describe('api/account_management/resetPassword', () => {
   });
 });
 
+describe('api/account_management/linkEmailPassword', () => {
+  const request = {
+    idToken: 'id-token',
+    returnSecureToken: true,
+    email: 'test@foo.com',
+    password: 'new-password'
+  };
+
+  let auth: TestAuth;
+
+  beforeEach(async () => {
+    auth = await testAuth();
+    mockFetch.setUp();
+  });
+
+  afterEach(mockFetch.tearDown);
+
+  it('should POST to the correct endpoint', async () => {
+    const mock = mockEndpoint(Endpoint.SIGN_UP, {
+      idToken: 'id-token'
+    });
+
+    const response = await linkEmailPassword(auth, request);
+    expect(response.idToken).to.eq('id-token');
+    expect(mock.calls[0].request).to.eql(request);
+    expect(mock.calls[0].method).to.eq('POST');
+    expect(mock.calls[0].headers!.get(HttpHeader.CONTENT_TYPE)).to.eq(
+      'application/json'
+    );
+    expect(mock.calls[0].headers!.get(HttpHeader.X_CLIENT_VERSION)).to.eq(
+      'testSDK/0.0.0'
+    );
+  });
+
+  it('should handle errors', async () => {
+    const mock = mockEndpoint(
+      Endpoint.SIGN_UP,
+      {
+        error: {
+          code: 400,
+          message: ServerError.INVALID_EMAIL,
+          errors: [
+            {
+              message: ServerError.INVALID_EMAIL
+            }
+          ]
+        }
+      },
+      400
+    );
+
+    await expect(linkEmailPassword(auth, request)).to.be.rejectedWith(
+      FirebaseError,
+      'Firebase: The email address is badly formatted. (auth/invalid-email).'
+    );
+    expect(mock.calls[0].request).to.eql(request);
+  });
+});
+
 describe('api/account_management/updateEmailPassword', () => {
   const request = {
     idToken: 'id-token',
diff --git a/packages/auth/src/api/account_management/email_and_password.ts b/packages/auth/src/api/account_management/email_and_password.ts
index 7d6f4ab84c8..a2429659b30 100644
--- a/packages/auth/src/api/account_management/email_and_password.ts
+++ b/packages/auth/src/api/account_management/email_and_password.ts
@@ -69,6 +69,18 @@ export async function updateEmailPassword(
   >(auth, HttpMethod.POST, Endpoint.SET_ACCOUNT_INFO, request);
 }
 
+// Used for linking an email/password account to an existing idToken. Uses the same request/response
+// format as updateEmailPassword.
+export async function linkEmailPassword(
+  auth: Auth,
+  request: UpdateEmailPasswordRequest
+): Promise<UpdateEmailPasswordResponse> {
+  return _performApiRequest<
+    UpdateEmailPasswordRequest,
+    UpdateEmailPasswordResponse
+  >(auth, HttpMethod.POST, Endpoint.SIGN_UP, request);
+}
+
 export interface ApplyActionCodeRequest {
   oobCode: string;
   tenantId?: string;
diff --git a/packages/auth/src/core/credentials/email.test.ts b/packages/auth/src/core/credentials/email.test.ts
index f3e6ae4966f..74d7cba94b3 100644
--- a/packages/auth/src/core/credentials/email.test.ts
+++ b/packages/auth/src/core/credentials/email.test.ts
@@ -288,8 +288,8 @@ describe('core/credentials/email', () => {
     });
 
     describe('#_linkToIdToken', () => {
-      it('calls update email password', async () => {
-        apiMock = mockEndpoint(Endpoint.SET_ACCOUNT_INFO, {
+      it('calls sign up with email password', async () => {
+        apiMock = mockEndpoint(Endpoint.SIGN_UP, {
           idToken: 'id-token',
           refreshToken: 'refresh-token',
           expiresIn: '1234',
diff --git a/packages/auth/src/core/credentials/email.ts b/packages/auth/src/core/credentials/email.ts
index 6421f33b5a1..69c4c119628 100644
--- a/packages/auth/src/core/credentials/email.ts
+++ b/packages/auth/src/core/credentials/email.ts
@@ -17,7 +17,10 @@
 
 import { ProviderId, SignInMethod } from '../../model/enums';
 
-import { updateEmailPassword } from '../../api/account_management/email_and_password';
+import {
+  linkEmailPassword,
+  updateEmailPassword
+} from '../../api/account_management/email_and_password';
 import {
   signInWithPassword,
   SignInWithPasswordRequest
@@ -166,7 +169,7 @@ export class EmailAuthCredential extends AuthCredential {
   ): Promise<IdTokenResponse> {
     switch (this.signInMethod) {
       case SignInMethod.EMAIL_PASSWORD:
-        return updateEmailPassword(auth, {
+        return linkEmailPassword(auth, {
           idToken,
           returnSecureToken: true,
           email: this._email,