diff --git a/spec/src/constructorio.js b/spec/src/constructorio.js
index 989a794b..450ac0d5 100644
--- a/spec/src/constructorio.js
+++ b/spec/src/constructorio.js
@@ -918,6 +918,22 @@ if (!bundled) {
         expect(instance.options).to.have.property('sessionId').to.deep.equal(newSessionId);
       });
 
+      it('Should use additionalTrackingKeys updated via setClientOptions in a DOM-less context', () => {
+        const instance = new ConstructorIO({
+          apiKey: validApiKey,
+          clientId,
+          sessionId: 1,
+        });
+
+        expect(instance.options.additionalTrackingKeys).to.be.undefined;
+
+        instance.setClientOptions({
+          additionalTrackingKeys: ['extra-key-1', 'extra-key-2'],
+        });
+
+        expect(instance.options).to.have.property('additionalTrackingKeys').to.deep.equal(['extra-key-1', 'extra-key-2']);
+      });
+
       it('Should update the options for modules with new session id in a DOM-less context', () => {
         const oldSessionId = 1;
         const newSessionId = 2;
diff --git a/spec/src/modules/tracker.js b/spec/src/modules/tracker.js
index 18cb9443..fb399ec8 100644
--- a/spec/src/modules/tracker.js
+++ b/spec/src/modules/tracker.js
@@ -17318,4 +17318,87 @@ describe(`ConstructorIO - Tracker${bundledDescriptionSuffix}`, () => {
       ).to.equal(true);
     });
   });
+
+  describe('additionalTrackingKeys', () => {
+    it('Should send tracking events to both primary and additional keys', (done) => {
+      const additionalKey = 'extra-test-key';
+      const { tracker } = new ConstructorIO({
+        apiKey: testApiKey,
+        fetch: fetchSpy,
+        ...requestQueueOptions,
+        additionalTrackingKeys: [additionalKey],
+      });
+
+      let callCount = 0;
+
+      const checkComplete = () => {
+        callCount += 1;
+
+        if (callCount === 2) {
+          expect(fetchSpy).to.have.been.calledTwice;
+
+          const firstCallUrl = fetchSpy.getCall(0).args[0];
+          const secondCallUrl = fetchSpy.getCall(1).args[0];
+
+          expect(firstCallUrl).to.contain(`key=${testApiKey}`);
+          expect(secondCallUrl).to.contain(`key=${additionalKey}`);
+          expect(secondCallUrl).to.not.contain(`key=${testApiKey}`);
+
+          done();
+        }
+      };
+
+      tracker.on('success', checkComplete);
+      tracker.on('error', checkComplete);
+
+      expect(tracker.trackSessionStartV2()).to.equal(true);
+    });
+
+    it('Should send identical request bodies for primary and additional keys', (done) => {
+      const additionalKey = 'extra-test-key';
+      const { tracker } = new ConstructorIO({
+        apiKey: testApiKey,
+        fetch: fetchSpy,
+        ...requestQueueOptions,
+        additionalTrackingKeys: [additionalKey],
+      });
+
+      let callCount = 0;
+
+      const checkComplete = () => {
+        callCount += 1;
+
+        if (callCount === 2) {
+          expect(fetchSpy).to.have.been.calledTwice;
+
+          const firstCallOptions = fetchSpy.getCall(0).args[1];
+          const secondCallOptions = fetchSpy.getCall(1).args[1];
+
+          const firstBody = JSON.parse(firstCallOptions.body);
+          const secondBody = JSON.parse(secondCallOptions.body);
+
+          expect(firstBody.key).to.equal(testApiKey);
+          expect(secondBody.key).to.equal(additionalKey);
+
+          const secondCallUrl = fetchSpy.getCall(1).args[0];
+          expect(secondCallUrl).to.not.contain(`key=${testApiKey}`);
+
+          // Verify bodies are the same except for the key
+          const firstBodyWithoutKey = { ...firstBody };
+          const secondBodyWithoutKey = { ...secondBody };
+          delete firstBodyWithoutKey.key;
+          delete secondBodyWithoutKey.key;
+
+          expect(firstBodyWithoutKey).to.deep.equal(secondBodyWithoutKey);
+
+          done();
+        }
+      };
+
+      tracker.on('success', checkComplete);
+      tracker.on('error', checkComplete);
+
+      expect(tracker.trackInputFocusV2('test query')).to.equal(true);
+    });
+  });
 });
diff --git a/spec/src/utils/request-queue.js b/spec/src/utils/request-queue.js
index 767e5bed..51f612f2 100644
--- a/spec/src/utils/request-queue.js
+++ b/spec/src/utils/request-queue.js
@@ -318,6 +318,137 @@ describe('ConstructorIO - Utils - Request Queue', function utilsRequestQueue() {
       });
     });
 
+    describe('additionalTrackingKeys', () => {
+      let defaultAgent;
+      let cleanup;
+
+      before(() => {
+        helpers.clearStorage();
+      });
+
+      beforeEach(() => {
+        global.CLIENT_VERSION = 'cio-mocha';
+        cleanup = jsdom();
+        defaultAgent = window.navigator.userAgent;
+      });
+
+      afterEach(() => {
+        window.navigator.__defineGetter__('userAgent', () => defaultAgent);
+        delete global.CLIENT_VERSION;
+        cleanup();
+        helpers.clearStorage();
+      });
+
+      it('Should add duplicate requests for each additional tracking key', () => {
+        store.session.set(humanityStorageKey, true);
+        const requests = new RequestQueue({
+          sendTrackingEvents: true,
+          trackingSendDelay: 1,
+          apiKey: 'primary-key',
+          additionalTrackingKeys: ['extra-key-1', 'extra-key-2'],
+        });
+
+        requests.queue('https://ac.cnstrc.com/behavior?action=session_start&key=primary-key&_dt=123', 'POST', { action: 'session_start', key: 'primary-key' });
+
+        const queue = RequestQueue.get();
+        expect(queue).to.be.an('array').length(3);
+
+        // Primary request
+        expect(queue[0].url).to.contain('key=primary-key');
+        expect(queue[0].body.key).to.equal('primary-key');
+
+        // First additional key
+        expect(queue[1].url).to.contain('key=extra-key-1');
+        expect(queue[1].url).to.not.contain('key=primary-key');
+        expect(queue[1].body.key).to.equal('extra-key-1');
+
+        // Second additional key
+        expect(queue[2].url).to.contain('key=extra-key-2');
+        expect(queue[2].url).to.not.contain('key=primary-key');
+        expect(queue[2].body.key).to.equal('extra-key-2');
+      });
+
+      it('Should not add duplicates when additionalTrackingKeys is an empty array', () => {
+        store.session.set(humanityStorageKey, true);
+        const requests = new RequestQueue({
+          sendTrackingEvents: true,
+          trackingSendDelay: 1,
+          apiKey: 'primary-key',
+          additionalTrackingKeys: [],
+        });
+
+        requests.queue('https://ac.cnstrc.com/behavior?action=session_start&key=primary-key&_dt=123');
+
+        expect(RequestQueue.get()).to.be.an('array').length(1);
+      });
+
+      it('Should not add duplicates when additionalTrackingKeys is not provided', () => {
+        store.session.set(humanityStorageKey, true);
+        const requests = new RequestQueue({
+          sendTrackingEvents: true,
+          trackingSendDelay: 1,
+          apiKey: 'primary-key',
+        });
+
+        requests.queue('https://ac.cnstrc.com/behavior?action=session_start&key=primary-key&_dt=123');
+
+        expect(RequestQueue.get()).to.be.an('array').length(1);
+      });
+
+      it('Should add duplicate requests for GET method', () => {
+        store.session.set(humanityStorageKey, true);
+        const requests = new RequestQueue({
+          sendTrackingEvents: true,
+          trackingSendDelay: 1,
+          apiKey: 'primary-key',
+          additionalTrackingKeys: ['extra-key-1'],
+        });
+
+        requests.queue('https://ac.cnstrc.com/behavior?action=session_start&key=primary-key&_dt=123');
+
+        const queue = RequestQueue.get();
+        expect(queue).to.be.an('array').length(2);
+
+        expect(queue[0].url).to.contain('key=primary-key');
+        expect(queue[1].url).to.contain('key=extra-key-1');
+        expect(queue[1].url).to.contain('action=session_start');
+      });
+
+      it('Should skip invalid entries in additionalTrackingKeys', () => {
+        store.session.set(humanityStorageKey, true);
+        const requests = new RequestQueue({
+          sendTrackingEvents: true,
+          trackingSendDelay: 1,
+          apiKey: 'primary-key',
+          additionalTrackingKeys: ['valid-key', '', null, 123, 'another-valid-key'],
+        });
+
+        requests.queue('https://ac.cnstrc.com/behavior?action=session_start&key=primary-key&_dt=123', 'POST', { action: 'session_start', key: 'primary-key' });
+
+        const queue = RequestQueue.get();
+        expect(queue).to.be.an('array').length(3);
+        expect(queue[1].url).to.contain('key=valid-key');
+        expect(queue[2].url).to.contain('key=another-valid-key');
+      });
+
+      it('Should not duplicate events when additionalTrackingKeys contains the primary key or duplicates', () => {
+        store.session.set(humanityStorageKey, true);
+        const requests = new RequestQueue({
+          sendTrackingEvents: true,
+          trackingSendDelay: 1,
+          apiKey: 'primary-key',
+          additionalTrackingKeys: ['extra-key', 'primary-key', 'extra-key'],
+        });
+
+        requests.queue('https://ac.cnstrc.com/behavior?action=session_start&key=primary-key&_dt=123', 'POST', { action: 'session_start', key: 'primary-key' });
+
+        const queue = RequestQueue.get();
+        expect(queue).to.be.an('array').length(2);
+        expect(queue[0].url).to.contain('key=primary-key');
+        expect(queue[1].url).to.contain('key=extra-key');
+      });
+    });
+
     describe('send', () => {
       let fetchSpy = null;
       let cleanup;
diff --git a/src/constructorio.js b/src/constructorio.js
index 7572724c..5e215f82 100644
--- a/src/constructorio.js
+++ b/src/constructorio.js
@@ -61,6 +61,7 @@ class ConstructorIO {
    * @param {number} [parameters.networkParameters.timeout] - Request timeout (in milliseconds) - may be overridden within individual method calls
    * @param {string} [parameters.humanityCheckLocation='session'] - Storage location for the humanity check flag ('session' for sessionStorage, 'local' for localStorage)
    * @param {boolean} [parameters.useWindowParameters=false] - Indicates if window globals (cnstrc/cnstrcUserId/cnstrcTestCells/cnstrcUserSegments) should be used as fallback for userId, testCells, and segments
+   * @param {string[]} [parameters.additionalTrackingKeys] - Additional API keys that each receive a duplicate of every tracking event. Events are always sent to the primary `apiKey` and, in addition, to every key in this array.
    * @property {object} search - Interface to {@link module:search}
    * @property {object} browse - Interface to {@link module:browse}
    * @property {object} autocomplete - Interface to {@link module:autocomplete}
@@ -97,6 +98,7 @@ class ConstructorIO {
       networkParameters,
       humanityCheckLocation,
       useWindowParameters,
+      additionalTrackingKeys,
     } = options;
 
     if (!apiKey || typeof apiKey !== 'string') {
@@ -147,6 +149,7 @@ class ConstructorIO {
       networkParameters: networkParameters || {},
       humanityCheckLocation: humanityCheckLocation || 'session',
       useWindowParameters: useWindowParameters === true,
+      additionalTrackingKeys,
     };
 
     if (useWindowParameters === true) {
@@ -179,10 +182,11 @@ class ConstructorIO {
    * @param {string} [options.userId] - User ID
    * @param {boolean} [options.sendTrackingEvents] - Indicates if tracking events should be dispatched
    * @param {string} [options.serviceUrl] - API URL endpoint (normalized to include an HTTPS protocol and strip a trailing slash)
+   * @param {string[]} [options.additionalTrackingKeys] - Additional API keys that each receive a duplicate of every tracking event. Events are always sent to the primary `apiKey` and, in addition, to every key in this array.
    */
   setClientOptions(options) {
     if (Object.keys(options).length) {
-      const { apiKey, segments, testCells, sessionId, userId, sendTrackingEvents, serviceUrl } = options;
+      const { apiKey, segments, testCells, sessionId, userId, sendTrackingEvents, serviceUrl, additionalTrackingKeys } = options;
 
       if (apiKey) {
         this.options.apiKey = apiKey;
@@ -214,6 +218,10 @@ class ConstructorIO {
         const formattedServiceUrl = helpers.addHTTPSToString(normalizedServiceUrl, this.options.allowHttpServiceUrl);
         this.options.serviceUrl = formattedServiceUrl || this.options.serviceUrl;
       }
+
+      if (Array.isArray(additionalTrackingKeys)) {
+        this.options.additionalTrackingKeys = additionalTrackingKeys;
+      }
     }
   }
 }
diff --git a/src/types/index.d.ts b/src/types/index.d.ts
index ebd8d241..68d678aa 100644
--- a/src/types/index.d.ts
+++ b/src/types/index.d.ts
@@ -73,6 +73,7 @@ export interface ConstructorClientOptions {
   networkParameters?: NetworkParameters;
   humanityCheckLocation?: 'session' | 'local';
   useWindowParameters?: boolean;
+  additionalTrackingKeys?: string[];
 }
 
 export interface RequestFeature extends Record<string, any> {
diff --git a/src/utils/request-queue.js b/src/utils/request-queue.js
index 291d0724..18c9ddbb 100644
--- a/src/utils/request-queue.js
+++ b/src/utils/request-queue.js
@@ -53,6 +53,30 @@ class RequestQueue {
         body,
         networkParameters,
       });
+
+      // Duplicate request for each additional tracking key
+      const additionalKeys = this.options?.additionalTrackingKeys;
+
+      if (Array.isArray(additionalKeys) && additionalKeys.length) {
+        const encodedOriginalKey = helpers.encodeURIComponentRFC3986(this.options.apiKey);
+
+        const uniqueKeys = new Set(
+          additionalKeys.filter((key) => key && typeof key === 'string' && key !== this.options.apiKey),
+        );
+
+        uniqueKeys.forEach((additionalKey) => {
+          const encodedAdditionalKey = helpers.encodeURIComponentRFC3986(additionalKey);
+          const swappedUrl = url.replace(`key=${encodedOriginalKey}`, `key=${encodedAdditionalKey}`);
+
+          queue.push({
+            url: obfuscatePiiRequest(swappedUrl),
+            method,
+            body: { ...body, key: additionalKey },
+            networkParameters,
+          });
+        });
+      }
+
       RequestQueue.set(queue);
     }
   }