diff --git a/packages/opentelemetry-web/src/enums/PerformanceTimingNames.ts b/packages/opentelemetry-web/src/enums/PerformanceTimingNames.ts
index 846a9ba967e..979b832d9a5 100644
--- a/packages/opentelemetry-web/src/enums/PerformanceTimingNames.ts
+++ b/packages/opentelemetry-web/src/enums/PerformanceTimingNames.ts
@@ -32,6 +32,7 @@ export enum PerformanceTimingNames {
   RESPONSE_END = 'responseEnd',
   RESPONSE_START = 'responseStart',
   SECURE_CONNECTION_START = 'secureConnectionStart',
+  TRANSFER_SIZE = 'transferSize',
   UNLOAD_EVENT_END = 'unloadEventEnd',
   UNLOAD_EVENT_START = 'unloadEventStart',
 }
diff --git a/packages/opentelemetry-web/src/types.ts b/packages/opentelemetry-web/src/types.ts
index 10ee04f14ec..0e11312c1e3 100644
--- a/packages/opentelemetry-web/src/types.ts
+++ b/packages/opentelemetry-web/src/types.ts
@@ -33,6 +33,7 @@ export type PerformanceEntries = {
   [PerformanceTimingNames.RESPONSE_END]?: number;
   [PerformanceTimingNames.RESPONSE_START]?: number;
   [PerformanceTimingNames.SECURE_CONNECTION_START]?: number;
+  [PerformanceTimingNames.TRANSFER_SIZE]?: number;
   [PerformanceTimingNames.UNLOAD_EVENT_END]?: number;
   [PerformanceTimingNames.UNLOAD_EVENT_START]?: number;
 };
diff --git a/packages/opentelemetry-web/src/utils.ts b/packages/opentelemetry-web/src/utils.ts
index aa3dd320b69..55f2606a230 100644
--- a/packages/opentelemetry-web/src/utils.ts
+++ b/packages/opentelemetry-web/src/utils.ts
@@ -81,6 +81,9 @@ export function addSpanNetworkEvents(
   addSpanNetworkEvent(span, PTN.REQUEST_START, resource);
   addSpanNetworkEvent(span, PTN.RESPONSE_START, resource);
   addSpanNetworkEvent(span, PTN.RESPONSE_END, resource);
+  if (resource.transferSize) {
+    span.setAttribute('transferSize', resource.transferSize);
+  }
 }
 
 /**
diff --git a/packages/opentelemetry-web/test/utils.test.ts b/packages/opentelemetry-web/test/utils.test.ts
index 805986de71e..c9ea9822474 100644
--- a/packages/opentelemetry-web/test/utils.test.ts
+++ b/packages/opentelemetry-web/test/utils.test.ts
@@ -137,8 +137,10 @@ describe('utils', () => {
   describe('addSpanNetworkEvents', () => {
     it('should add all network events to span', () => {
       const addEventSpy = sinon.spy();
+      const setAttributeSpy = sinon.spy();
       const span = ({
         addEvent: addEventSpy,
+        setAttribute: setAttributeSpy,
       } as unknown) as tracing.Span;
       const entries = {
         [PTN.FETCH_START]: 123,
@@ -150,6 +152,7 @@ describe('utils', () => {
         [PTN.REQUEST_START]: 123,
         [PTN.RESPONSE_START]: 123,
         [PTN.RESPONSE_END]: 123,
+        [PTN.TRANSFER_SIZE]: 123,
       } as PerformanceEntries;
 
       assert.strictEqual(addEventSpy.callCount, 0);
@@ -157,6 +160,7 @@ describe('utils', () => {
       addSpanNetworkEvents(span, entries);
 
       assert.strictEqual(addEventSpy.callCount, 9);
+      assert.strictEqual(setAttributeSpy.callCount, 1);
     });
   });
   describe('addSpanNetworkEvent', () => {