diff --git a/src/app/credential-internal.ts b/src/app/credential-internal.ts
index 2d240cc301..c8ce25b246 100644
--- a/src/app/credential-internal.ts
+++ b/src/app/credential-internal.ts
@@ -39,6 +39,7 @@ export class ApplicationDefaultCredential implements Credential {
   private readonly googleAuth: GoogleAuth;
   private authClient: AnyAuthClient;
   private projectId?: string;
+  private quotaProjectId?: string;
   private accountId?: string;
 
   constructor(httpAgent?: Agent) {
@@ -58,6 +59,7 @@ export class ApplicationDefaultCredential implements Credential {
     }
     await this.authClient.getAccessToken();
     const credentials = this.authClient.credentials;
+    this.quotaProjectId = this.authClient.quotaProjectId;
     return populateCredential(credentials);
   }
 
@@ -68,6 +70,13 @@ export class ApplicationDefaultCredential implements Credential {
     return Promise.resolve(this.projectId);
   }
 
+  public getQuotaProjectId(): string | undefined {
+    if (!this.quotaProjectId) {
+      this.quotaProjectId = this.authClient?.quotaProjectId;
+    }
+    return this.quotaProjectId;
+  }
+
   public async isComputeEngineCredential(): Promise<boolean> {
     if (!this.authClient) {
       this.authClient = await this.googleAuth.getClient();
diff --git a/src/utils/api-request.ts b/src/utils/api-request.ts
index d64e0a2762..c5e284e414 100644
--- a/src/utils/api-request.ts
+++ b/src/utils/api-request.ts
@@ -26,6 +26,7 @@ import url = require('url');
 import { EventEmitter } from 'events';
 import { Readable } from 'stream';
 import * as zlibmod from 'zlib';
+import { ApplicationDefaultCredential } from '../app/credential-internal';
 import { getMetricsHeader } from '../utils/index';
 
 /** Http method type definition. */
@@ -1077,10 +1078,13 @@ export class AuthorizedHttpClient extends HttpClient {
       const authHeader = 'Authorization';
       requestCopy.headers[authHeader] = `Bearer ${token}`;
 
-      // Fix issue where firebase-admin does not specify quota project that is
-      // necessary for use when utilizing human account with ADC (RSDF)
-      if (!requestCopy.headers['x-goog-user-project'] && this.app.options.projectId) {
-        requestCopy.headers['x-goog-user-project'] = this.app.options.projectId
+      let quotaProjectId: string | undefined;
+      if (this.app.options.credential instanceof ApplicationDefaultCredential) {
+        quotaProjectId = this.app.options.credential.getQuotaProjectId();
+      }
+      quotaProjectId = process.env.GOOGLE_CLOUD_QUOTA_PROJECT || quotaProjectId;
+      if (!requestCopy.headers['x-goog-user-project'] && validator.isNonEmptyString(quotaProjectId)) {
+        requestCopy.headers['x-goog-user-project'] = quotaProjectId;
       }
 
       if (!requestCopy.httpAgent && this.app.options.httpAgent) {
@@ -1112,6 +1116,15 @@ export class AuthorizedHttp2Client extends Http2Client {
       const authHeader = 'Authorization';
       requestCopy.headers[authHeader] = `Bearer ${token}`;
 
+      let quotaProjectId: string | undefined;
+      if (this.app.options.credential instanceof ApplicationDefaultCredential) {
+        quotaProjectId = this.app.options.credential.getQuotaProjectId();
+      }
+      quotaProjectId = process.env.GOOGLE_CLOUD_QUOTA_PROJECT || quotaProjectId;
+      if (!requestCopy.headers['x-goog-user-project'] && validator.isNonEmptyString(quotaProjectId)) {
+        requestCopy.headers['x-goog-user-project'] = quotaProjectId;
+      }
+
       requestCopy.headers['X-Goog-Api-Client'] = getMetricsHeader()
 
       return super.send(requestCopy);
diff --git a/test/unit/app-check/app-check-api-client-internal.spec.ts b/test/unit/app-check/app-check-api-client-internal.spec.ts
index 3f2746cf59..743f6ed89f 100644
--- a/test/unit/app-check/app-check-api-client-internal.spec.ts
+++ b/test/unit/app-check/app-check-api-client-internal.spec.ts
@@ -45,7 +45,6 @@ describe('AppCheckApiClient', () => {
   const EXPECTED_HEADERS = {
     'Authorization': 'Bearer mock-token',
     'X-Firebase-Client': `fire-admin-node/${getSdkVersion()}`,
-    'x-goog-user-project': 'test-project',
     'X-Goog-Api-Client': getMetricsHeader(),
   };
 
diff --git a/test/unit/data-connect/data-connect-api-client-internal.spec.ts b/test/unit/data-connect/data-connect-api-client-internal.spec.ts
index 0815515204..93b7120703 100644
--- a/test/unit/data-connect/data-connect-api-client-internal.spec.ts
+++ b/test/unit/data-connect/data-connect-api-client-internal.spec.ts
@@ -43,7 +43,6 @@ describe('DataConnectApiClient', () => {
   const EXPECTED_HEADERS = {
     'Authorization': 'Bearer mock-token',
     'X-Firebase-Client': `fire-admin-node/${getSdkVersion()}`,
-    'x-goog-user-project': 'test-project',
     'X-Goog-Api-Client': getMetricsHeader(),
   };
 
diff --git a/test/unit/extensions/extensions-api-client-internal.spec.ts b/test/unit/extensions/extensions-api-client-internal.spec.ts
index 32213b8068..66f2e8198b 100644
--- a/test/unit/extensions/extensions-api-client-internal.spec.ts
+++ b/test/unit/extensions/extensions-api-client-internal.spec.ts
@@ -43,7 +43,6 @@ describe('Extension API client', () => {
   const EXPECTED_HEADERS = {
     'Authorization': 'Bearer mock-token',
     'X-Firebase-Client': `fire-admin-node/${getSdkVersion()}`,
-    'x-goog-user-project': 'test-project',
     'X-Goog-Api-Client': getMetricsHeader(),
   }
   
diff --git a/test/unit/functions/functions-api-client-internal.spec.ts b/test/unit/functions/functions-api-client-internal.spec.ts
index 40e24b1fea..15862d57b2 100644
--- a/test/unit/functions/functions-api-client-internal.spec.ts
+++ b/test/unit/functions/functions-api-client-internal.spec.ts
@@ -46,7 +46,6 @@ describe('FunctionsApiClient', () => {
   const EXPECTED_HEADERS = {
     'X-Firebase-Client': `fire-admin-node/${getSdkVersion()}`,
     'Authorization': 'Bearer mock-token',
-    'x-goog-user-project': 'test-project',
     'X-Goog-Api-Client': getMetricsHeader(),
   };
 
diff --git a/test/unit/machine-learning/machine-learning-api-client.spec.ts b/test/unit/machine-learning/machine-learning-api-client.spec.ts
index c77380f2f3..2f4447c2da 100644
--- a/test/unit/machine-learning/machine-learning-api-client.spec.ts
+++ b/test/unit/machine-learning/machine-learning-api-client.spec.ts
@@ -117,7 +117,6 @@ describe('MachineLearningApiClient', () => {
   const EXPECTED_HEADERS = {
     'Authorization': 'Bearer mock-token',
     'X-Firebase-Client': `fire-admin-node/${getSdkVersion()}`,
-    'x-goog-user-project': 'test-project',
     'X-Goog-Api-Client': getMetricsHeader(),
   };
   const noProjectId = 'Failed to determine project ID. Initialize the SDK with service '
diff --git a/test/unit/remote-config/remote-config-api-client.spec.ts b/test/unit/remote-config/remote-config-api-client.spec.ts
index 9b6b8709bf..91783e9088 100644
--- a/test/unit/remote-config/remote-config-api-client.spec.ts
+++ b/test/unit/remote-config/remote-config-api-client.spec.ts
@@ -57,7 +57,6 @@ describe('RemoteConfigApiClient', () => {
     'Authorization': 'Bearer mock-token',
     'X-Firebase-Client': `fire-admin-node/${getSdkVersion()}`,
     'Accept-Encoding': 'gzip',
-    'x-goog-user-project': 'test-project',
     'X-Goog-Api-Client': getMetricsHeader(),
   };
 
diff --git a/test/unit/security-rules/security-rules-api-client.spec.ts b/test/unit/security-rules/security-rules-api-client.spec.ts
index 2c1c8d9ec0..c4176540a6 100644
--- a/test/unit/security-rules/security-rules-api-client.spec.ts
+++ b/test/unit/security-rules/security-rules-api-client.spec.ts
@@ -44,7 +44,6 @@ describe('SecurityRulesApiClient', () => {
   const EXPECTED_HEADERS = {
     'Authorization': 'Bearer mock-token',
     'X-Firebase-Client': `fire-admin-node/${getSdkVersion()}`,
-    'x-goog-user-project': 'test-project',
     'X-Goog-Api-Client': getMetricsHeader(),
   };
   const noProjectId = 'Failed to determine project ID. Initialize the SDK with service '
diff --git a/test/unit/utils/api-request.spec.ts b/test/unit/utils/api-request.spec.ts
index 4fcb5a397b..d64589f8c9 100644
--- a/test/unit/utils/api-request.spec.ts
+++ b/test/unit/utils/api-request.spec.ts
@@ -17,6 +17,7 @@
 
 'use strict';
 
+import * as _ from 'lodash';
 import * as chai from 'chai';
 import * as nock from 'nock';
 import * as sinon from 'sinon';
@@ -35,6 +36,7 @@ import {
 import { deepCopy } from '../../../src/utils/deep-copy';
 import { Agent } from 'http';
 import * as zlib from 'zlib';
+import { getMetricsHeader } from '../../../src/utils';
 
 chai.should();
 chai.use(sinonChai);
@@ -2648,6 +2650,45 @@ describe('AuthorizedHttpClient', () => {
     });
   });
 
+  describe('Quota Project', () => {
+    let stubs: sinon.SinonStub[] = [];
+
+    afterEach(() => {
+      _.forEach(stubs, (stub) => stub.restore());
+      stubs = [];
+      if (process.env.GOOGLE_CLOUD_QUOTA_PROJECT) {
+        delete process.env.GOOGLE_CLOUD_QUOTA_PROJECT;
+      }
+    });
+
+    it('should include quota project id in headers when GOOGLE_CLOUD_QUOTA_PROJECT is set', () => {
+      const reqData = { request: 'data' };
+      const stub = sinon
+        .stub(HttpClient.prototype, 'send')
+        .resolves(utils.responseFrom({}, 200));
+      stubs.push(stub);
+      process.env.GOOGLE_CLOUD_QUOTA_PROJECT = 'test-project-id';
+      const client = new AuthorizedHttpClient(mockApp);
+      return client.send({
+        method: 'POST',
+        url: mockUrl,
+        data: reqData,
+      })
+        .then(() => {
+          expect(stub).to.have.been.calledOnce.and.calledWith({
+            method: 'POST',
+            url: mockUrl,
+            headers: {
+              ...requestHeaders.reqheaders,
+              'x-goog-user-project': 'test-project-id',
+              'X-Goog-Api-Client': getMetricsHeader(),
+            },
+            data: reqData
+          });
+        });
+    });
+  });
+
   it('should not mutate the arguments', () => {
     const reqData = { request: 'data' };
     const options = {