diff --git a/src/eventarc/eventarc-client-internal.ts b/src/eventarc/eventarc-client-internal.ts
index a9fc162f7a..09ad5f9cf9 100644
--- a/src/eventarc/eventarc-client-internal.ts
+++ b/src/eventarc/eventarc-client-internal.ts
@@ -42,6 +42,7 @@ const DEFAULT_CHANNEL_REGION = 'us-central1';
  */
 export class EventarcApiClient {
   private readonly httpClient: HttpClient;
+  private readonly eventarcHost: string;
   private projectId?: string;
   private readonly resolvedChannelName: Promise<string>;
 
@@ -53,6 +54,7 @@ export class EventarcApiClient {
       });
     }
     this.httpClient = new AuthorizedHttpClient(app as FirebaseApp);
+    this.eventarcHost = process.env.CLOUD_EVENTARC_EMULATOR_HOST ?? EVENTARC_API;
     this.resolvedChannelName = this.resolveChannelName(channel.name);
   }
 
@@ -105,7 +107,7 @@ export class EventarcApiClient {
     }
     const request: HttpRequestConfig = {
       method: 'POST',
-      url: `${this.getEventarcHost()}/${channel}:publishEvents`,
+      url: `${this.eventarcHost}/${channel}:publishEvents`,
       data: JSON.stringify({ events }),
     };
     return this.sendRequest(request);
@@ -162,8 +164,4 @@ export class EventarcApiClient {
     const projectId = await this.getProjectId();
     return `projects/${projectId}/locations/${location}/channels/${channelId}`;
   }
-
-  private getEventarcHost(): string {
-    return process.env.CLOUD_EVENTARC_EMULATOR_HOST ?? EVENTARC_API;
-  }
 }
diff --git a/test/unit/eventarc/eventarc.spec.ts b/test/unit/eventarc/eventarc.spec.ts
index 55cc853b4a..2ecc4299c8 100644
--- a/test/unit/eventarc/eventarc.spec.ts
+++ b/test/unit/eventarc/eventarc.spec.ts
@@ -59,6 +59,8 @@ const TEST_EVENT2 : CloudEvent = {
 };
 const TEST_EVENT2_SERIALIZED = JSON.stringify(toCloudEventProtoFormat(TEST_EVENT2));
 
+const EMULATOR_HOST = 'http://127.0.0.1:9299';
+
 describe('eventarc', () => {
   let mockApp: FirebaseApp;
   let eventarc: Eventarc;
@@ -168,6 +170,84 @@ describe('eventarc', () => {
     });
   });
 
+  describe('emulator host', () => {
+    let mockAccessToken: string;
+    let httpStub: sinon.SinonStub;
+    let accessTokenStub: sinon.SinonStub;
+    let originalEmulatorHost: string | undefined;
+
+    before(() => {
+      mockAccessToken = utils.generateRandomAccessToken();
+      accessTokenStub = utils.stubGetAccessToken(mockAccessToken);
+      originalEmulatorHost = process.env.CLOUD_EVENTARC_EMULATOR_HOST;
+    });
+
+    after(() => {
+      accessTokenStub?.restore();
+      if (originalEmulatorHost === undefined) {
+        delete process.env.CLOUD_EVENTARC_EMULATOR_HOST;
+      } else {
+        process.env.CLOUD_EVENTARC_EMULATOR_HOST = originalEmulatorHost;
+      }
+    });
+
+    afterEach(() => {
+      httpStub?.restore();
+      delete process.env.CLOUD_EVENTARC_EMULATOR_HOST;
+    });
+
+    it('is resolved at construction time', async () => {
+      delete process.env.CLOUD_EVENTARC_EMULATOR_HOST;
+      const prodChannel = eventarc.channel();
+
+      process.env.CLOUD_EVENTARC_EMULATOR_HOST = EMULATOR_HOST;
+      const emulatorChannel = eventarc.channel();
+
+      delete process.env.CLOUD_EVENTARC_EMULATOR_HOST;
+
+      httpStub = sinon
+        .stub(HttpClient.prototype, 'send')
+        .resolves(utils.responseFrom({}));
+
+      await prodChannel.publish(TEST_EVENT1);
+      await emulatorChannel.publish(TEST_EVENT1);
+
+      expect(httpStub).to.have.been.calledTwice;
+      expect(httpStub.firstCall).to.have.been.calledWith({
+        method: 'POST',
+        url: 'https://eventarcpublishing.googleapis.com/v1/projects/project_id/locations/us-central1/channels/firebase:publishEvents',
+        data: `{"events":[${TEST_EVENT1_SERIALIZED}]}`,
+        headers: getExpectedHeaders(mockAccessToken)
+      });
+      expect(httpStub.secondCall).to.have.been.calledWith({
+        method: 'POST',
+        url: `${EMULATOR_HOST}/projects/project_id/locations/us-central1/channels/firebase:publishEvents`,
+        data: `{"events":[${TEST_EVENT1_SERIALIZED}]}`,
+        headers: getExpectedHeaders(mockAccessToken)
+      });
+    });
+
+    it('is not picked up by a channel created before it was set', async () => {
+      delete process.env.CLOUD_EVENTARC_EMULATOR_HOST;
+      const prodChannel = eventarc.channel();
+
+      process.env.CLOUD_EVENTARC_EMULATOR_HOST = EMULATOR_HOST;
+
+      httpStub = sinon
+        .stub(HttpClient.prototype, 'send')
+        .resolves(utils.responseFrom({}));
+
+      await prodChannel.publish(TEST_EVENT1);
+
+      expect(httpStub).to.have.been.calledOnce.and.calledWith({
+        method: 'POST',
+        url: 'https://eventarcpublishing.googleapis.com/v1/projects/project_id/locations/us-central1/channels/firebase:publishEvents',
+        data: `{"events":[${TEST_EVENT1_SERIALIZED}]}`,
+        headers: getExpectedHeaders(mockAccessToken)
+      });
+    });
+  });
+
   describe('full resource name Channel', () => {
     let channel : Channel;
     let mockAccessToken: string;