diff --git a/sdk/core/core-amqp/CHANGELOG.md b/sdk/core/core-amqp/CHANGELOG.md
index cd01d485a28e..2b6f6441622b 100644
--- a/sdk/core/core-amqp/CHANGELOG.md
+++ b/sdk/core/core-amqp/CHANGELOG.md
@@ -2,6 +2,11 @@
 
 ## 2.0.0 (Unreleased)
 
+### Breaking changes
+
+- `DefaultDataTransformer` is no longer exported.
+  [PR 12320](https://github.com/Azure/azure-sdk-for-js/pull/12320)
+
 ## 2.0.0-beta.1 (2020-11-03)
 
 - `AmqpAnnotatedMessage` interface that closely represents the AMQP annotated message from the [AMQP spec](https://docs.oasis-open.org/amqp/core/v1.0/os/amqp-core-messaging-v1.0-os.html#section-message-format) has been added. New `AmqpMessageHeaders` and `AmqpMessageProperties` interfaces(properties with camelCasing) have been added in the place of re-exports from "rhea" library(properties with snake_casing).
diff --git a/sdk/core/core-amqp/review/core-amqp.api.md b/sdk/core/core-amqp/review/core-amqp.api.md
index 65e55292e054..003eeae84446 100644
--- a/sdk/core/core-amqp/review/core-amqp.api.md
+++ b/sdk/core/core-amqp/review/core-amqp.api.md
@@ -384,12 +384,6 @@ export interface DataTransformer {
     encode: (body: any) => any;
 }
 
-// @public
-export class DefaultDataTransformer implements DataTransformer {
-    decode(body: any): any;
-    encode(body: any): any;
-}
-
 // @public
 export const defaultLock: AsyncLock;
 
diff --git a/sdk/core/core-amqp/src/index.ts b/sdk/core/core-amqp/src/index.ts
index ca971e056b2c..95bc81054eea 100644
--- a/sdk/core/core-amqp/src/index.ts
+++ b/sdk/core/core-amqp/src/index.ts
@@ -5,7 +5,7 @@
 
 export { RequestResponseLink, SendRequestOptions } from "./requestResponseLink";
 export { retry, RetryOptions, RetryConfig, RetryOperationType, RetryMode } from "./retry";
-export { DataTransformer, DefaultDataTransformer } from "./dataTransformer";
+export { DataTransformer } from "./dataTransformer";
 export { TokenType } from "./auth/token";
 
 export { ConnectionConfig, ConnectionConfigOptions } from "./connectionConfig/connectionConfig";
diff --git a/sdk/core/core-amqp/test/context.spec.ts b/sdk/core/core-amqp/test/context.spec.ts
index 4c51c56b4910..d3dfe98c69f3 100644
--- a/sdk/core/core-amqp/test/context.spec.ts
+++ b/sdk/core/core-amqp/test/context.spec.ts
@@ -3,9 +3,10 @@
 
 import * as chai from "chai";
 const should = chai.should();
-import { CbsClient, ConnectionConfig, ConnectionContextBase, DefaultDataTransformer } from "../src";
+import { CbsClient, ConnectionConfig, ConnectionContextBase } from "../src";
 import { Connection } from "rhea-promise";
 import { isNode } from "../src/util/utils";
+import { DefaultDataTransformer } from "../src/dataTransformer";
 
 describe("ConnectionContextBase", function() {
   it("should be created with required parameters", function(done) {
diff --git a/sdk/core/core-amqp/test/dataTransformer.spec.ts b/sdk/core/core-amqp/test/dataTransformer.spec.ts
index 6c089822a4ef..a212847b6305 100644
--- a/sdk/core/core-amqp/test/dataTransformer.spec.ts
+++ b/sdk/core/core-amqp/test/dataTransformer.spec.ts
@@ -6,8 +6,7 @@ import * as chai from "chai";
 const should = chai.should();
 import * as assert from "assert";
 import isBuffer from "is-buffer";
-
-import { DefaultDataTransformer } from "../src";
+import { DefaultDataTransformer } from "../src/dataTransformer";
 
 describe("DataTransformer", function() {
   const objectBody: any = {
@@ -38,7 +37,7 @@ describe("DataTransformer", function() {
   const nullBody: null = null;
   const undefinedBody: undefined = undefined;
   const emptyStringBody: string = "";
-  const bufferbody: Buffer = Buffer.from("zzz", "utf8");
+  const bufferBody: Buffer = Buffer.from("zzz", "utf8");
   const hexBufferBody: Buffer = Buffer.from("7468697320697320612074c3a97374", "hex");
   const transformer = new DefaultDataTransformer();
 
@@ -115,11 +114,11 @@ describe("DataTransformer", function() {
   });
 
   it("should correctly encode/decode a buffer message body", function(done) {
-    const encoded: any = transformer.encode(bufferbody);
+    const encoded: any = transformer.encode(bufferBody);
     encoded.typecode.should.equal(117);
     isBuffer(encoded.content).should.equal(true);
     const decoded: any = transformer.decode(encoded);
-    assert.deepEqual(decoded, bufferbody);
+    assert.deepEqual(decoded, bufferBody);
     done();
   });
 
@@ -184,8 +183,8 @@ describe("DataTransformer", function() {
     });
 
     it("should correctly decode a buffer message body", function(done) {
-      const decoded: any = transformer.decode(bufferbody);
-      assert.deepEqual(decoded, bufferbody);
+      const decoded: any = transformer.decode(bufferBody);
+      assert.deepEqual(decoded, bufferBody);
       done();
     });
 
diff --git a/sdk/servicebus/service-bus/test/internal/unittestUtils.ts b/sdk/servicebus/service-bus/test/internal/unittestUtils.ts
index 8a35bc44e0e9..000f8b8b983a 100644
--- a/sdk/servicebus/service-bus/test/internal/unittestUtils.ts
+++ b/sdk/servicebus/service-bus/test/internal/unittestUtils.ts
@@ -8,7 +8,7 @@ import {
   ReceiverEvents,
   ReceiverOptions
 } from "rhea-promise";
-import { DefaultDataTransformer, Constants } from "@azure/core-amqp";
+import { Constants } from "@azure/core-amqp";
 import { AccessToken } from "@azure/core-auth";
 import { EventEmitter } from "events";
 import { getUniqueName } from "../../src/util/utils";
@@ -88,7 +88,10 @@ export function createConnectionContextForTests(
       },
       async close(): Promise<void> {}
     },
-    dataTransformer: new DefaultDataTransformer(),
+    dataTransformer: {
+      encode: (data: any) => data,
+      decode: (data: any) => data
+    },
     tokenCredential: {
       getToken() {
         return {