diff --git a/src/emulator/eventarcEmulator.ts b/src/emulator/eventarcEmulator.ts
index e08f9c358c5..b1f487a8914 100644
--- a/src/emulator/eventarcEmulator.ts
+++ b/src/emulator/eventarcEmulator.ts
@@ -8,6 +8,7 @@ import { EventTrigger } from "./functionsEmulatorShared";
 import { CloudEvent } from "./events/types";
 import { EmulatorRegistry } from "./registry";
 import { FirebaseError } from "../error";
+import { cloudEventFromProtoToJson } from "./eventarcEmulatorUtils";
 
 interface CustomEventTrigger {
   projectId: string;
@@ -123,7 +124,7 @@ export class EventarcEmulator implements EmulatorInstance {
             .request<CloudEvent<any>, NodeJS.ReadableStream>({
               method: "POST",
               path: `/functions/projects/${trigger.projectId}/triggers/${trigger.triggerName}`,
-              body: JSON.stringify(event),
+              body: JSON.stringify(cloudEventFromProtoToJson(event)),
               responseType: "stream",
               resolveOnHTTPError: true,
             })
diff --git a/src/emulator/eventarcEmulatorUtils.ts b/src/emulator/eventarcEmulatorUtils.ts
new file mode 100644
index 00000000000..3cc06f5a539
--- /dev/null
+++ b/src/emulator/eventarcEmulatorUtils.ts
@@ -0,0 +1,62 @@
+import { CloudEvent } from "./events/types";
+import { FirebaseError } from "../error";
+
+const BUILT_IN_ATTRS: string[] = ["time", "datacontenttype", "subject"];
+
+export function cloudEventFromProtoToJson(ce: any): CloudEvent<any> {
+  if (ce["id"] === undefined) {
+    throw new FirebaseError("CloudEvent 'id' is required.");
+  }
+  if (ce["type"] === undefined) {
+    throw new FirebaseError("CloudEvent 'type' is required.");
+  }
+  if (ce["specVersion"] === undefined) {
+    throw new FirebaseError("CloudEvent 'specVersion' is required.");
+  }
+  if (ce["source"] === undefined) {
+    throw new FirebaseError("CloudEvent 'source' is required.");
+  }
+  const out: CloudEvent<any> = {
+    id: ce["id"],
+    type: ce["type"],
+    specversion: ce["specVersion"],
+    source: ce["source"],
+    subject: getOptionalAttribute(ce, "subject", "ceString"),
+    time: getRequiredAttribute(ce, "time", "ceTimestamp"),
+    data: getData(ce),
+    datacontenttype: getRequiredAttribute(ce, "datacontenttype", "ceString"),
+  };
+  for (const attr in ce["attributes"]) {
+    if (BUILT_IN_ATTRS.includes(attr)) {
+      continue;
+    }
+    out[attr] = getRequiredAttribute(ce, attr, "ceString");
+  }
+  return out;
+}
+
+function getOptionalAttribute(ce: any, attr: string, type: string): string | undefined {
+  return ce["attributes"][attr][type];
+}
+
+function getRequiredAttribute(ce: any, attr: string, type: string): string {
+  const val = ce["attributes"][attr][type];
+  if (val === undefined) {
+    throw new FirebaseError("CloudEvent must contain " + attr + " attribute");
+  }
+  return val;
+}
+
+function getData(ce: any): any {
+  const contentType = getRequiredAttribute(ce, "datacontenttype", "ceString");
+  switch (contentType) {
+    case "application/json":
+      return JSON.parse(ce["textData"]);
+    case "text/plain":
+      return ce["textData"];
+    case undefined:
+      return undefined;
+    default:
+      throw new FirebaseError("Unsupported content type: " + contentType);
+  }
+}
diff --git a/src/test/emulators/eventarcEmulatorUtils.spec.ts b/src/test/emulators/eventarcEmulatorUtils.spec.ts
new file mode 100644
index 00000000000..d7015a11829
--- /dev/null
+++ b/src/test/emulators/eventarcEmulatorUtils.spec.ts
@@ -0,0 +1,126 @@
+import { expect } from "chai";
+
+import { cloudEventFromProtoToJson } from "../../emulator/eventarcEmulatorUtils";
+
+describe("eventarcEmulatorUtils", () => {
+  describe("cloudEventFromProtoToJson", () => {
+    it("converts cloud event from proto format", () => {
+      expect(
+        cloudEventFromProtoToJson({
+          "@type": "type.googleapis.com/io.cloudevents.v1.CloudEvent",
+          attributes: {
+            customattr: {
+              ceString: "custom value",
+            },
+            datacontenttype: {
+              ceString: "application/json",
+            },
+            time: {
+              ceTimestamp: "2022-03-16T20:20:42.212Z",
+            },
+            subject: {
+              ceString: "context",
+            },
+          },
+          id: "user-provided-id",
+          source: "/my/functions",
+          specVersion: "1.0",
+          textData: '{"hello":"world"}',
+          type: "some.custom.event",
+        })
+      ).to.deep.eq({
+        type: "some.custom.event",
+        specversion: "1.0",
+        subject: "context",
+        datacontenttype: "application/json",
+        id: "user-provided-id",
+        data: {
+          hello: "world",
+        },
+        source: "/my/functions",
+        time: "2022-03-16T20:20:42.212Z",
+        customattr: "custom value",
+      });
+    });
+
+    it("throws invalid argument when source not set", () => {
+      expect(() =>
+        cloudEventFromProtoToJson({
+          "@type": "type.googleapis.com/io.cloudevents.v1.CloudEvent",
+          attributes: {
+            customattr: {
+              ceString: "custom value",
+            },
+            datacontenttype: {
+              ceString: "application/json",
+            },
+            time: {
+              ceTimestamp: "2022-03-16T20:20:42.212Z",
+            },
+            subject: {
+              ceString: "context",
+            },
+          },
+          id: "user-provided-id",
+          specVersion: "1.0",
+          textData: '{"hello":"world"}',
+          type: "some.custom.event",
+        })
+      ).throws("CloudEvent 'source' is required.");
+    });
+
+    it("populates converts object data to JSON and sets datacontenttype", () => {
+      const got = cloudEventFromProtoToJson({
+        "@type": "type.googleapis.com/io.cloudevents.v1.CloudEvent",
+        attributes: {
+          customattr: {
+            ceString: "custom value",
+          },
+          datacontenttype: {
+            ceString: "application/json",
+          },
+          time: {
+            ceTimestamp: "2022-03-16T20:20:42.212Z",
+          },
+          subject: {
+            ceString: "context",
+          },
+        },
+        id: "user-provided-id",
+        source: "/my/functions",
+        specVersion: "1.0",
+        textData: '{"hello":"world"}',
+        type: "some.custom.event",
+      });
+      expect(got.datacontenttype).to.deep.eq("application/json");
+      expect(got.data).to.deep.eq({ hello: "world" });
+    });
+
+    it("populates string data and sets datacontenttype", () => {
+      const got = cloudEventFromProtoToJson({
+        "@type": "type.googleapis.com/io.cloudevents.v1.CloudEvent",
+        attributes: {
+          customattr: {
+            ceString: "custom value",
+          },
+          datacontenttype: {
+            ceString: "text/plain",
+          },
+          time: {
+            ceTimestamp: "2022-03-16T20:20:42.212Z",
+          },
+          subject: {
+            ceString: "context",
+          },
+        },
+        id: "user-provided-id",
+        source: "/my/functions",
+        specVersion: "1.0",
+        textData: "hello world",
+        type: "some.custom.event",
+      });
+      expect(got.datacontenttype).to.deep.eq("text/plain");
+      expect(got.data).to.eq("hello world");
+    });
+  });
+});