diff --git a/.changeset/fluffy-masks-cover.md b/.changeset/fluffy-masks-cover.md
new file mode 100644
index 00000000000..38ec989910e
--- /dev/null
+++ b/.changeset/fluffy-masks-cover.md
@@ -0,0 +1,5 @@
+---
+"@apollo/client": minor
+---
+
+Add onError prop to MockProvider
diff --git a/src/testing/core/index.ts b/src/testing/core/index.ts
index c03a7e8cf69..31974ebb154 100644
--- a/src/testing/core/index.ts
+++ b/src/testing/core/index.ts
@@ -1,5 +1,6 @@
 export {
   MockLink,
+  MockLinkData,
   mockSingleLink,
   MockedResponse,
   ResultFunction
diff --git a/src/testing/core/mocking/mockLink.ts b/src/testing/core/mocking/mockLink.ts
index 7d0086a4c51..72a77a63613 100644
--- a/src/testing/core/mocking/mockLink.ts
+++ b/src/testing/core/mocking/mockLink.ts
@@ -29,6 +29,13 @@ export interface MockedResponse<TData = Record<string, any>> {
   newData?: ResultFunction<FetchResult>;
 }
 
+export interface MockLinkData {
+  key: string;
+  mockedResponses: ReadonlyArray<MockedResponse>;
+  operation: Operation;
+  unmatchedVars: Array<Record<string, any>>;
+}
+
 function requestToKey(request: GraphQLRequest, addTypename: Boolean): string {
   const queryString =
     request.query &&
@@ -40,14 +47,19 @@ function requestToKey(request: GraphQLRequest, addTypename: Boolean): string {
 export class MockLink extends ApolloLink {
   public operation: Operation;
   public addTypename: Boolean = true;
+  public customErrorHandler: (error: Error, mockLinkData: MockLinkData) => Boolean;
   private mockedResponsesByKey: { [key: string]: MockedResponse[] } = {};
 
   constructor(
     mockedResponses: ReadonlyArray<MockedResponse>,
-    addTypename: Boolean = true
+    addTypename: Boolean = true,
+    customErrorHandler?: (error: Error, mockLinkData: MockLinkData) => Boolean,
   ) {
     super();
     this.addTypename = addTypename;
+    if (customErrorHandler) {
+      this.customErrorHandler = customErrorHandler;
+    }
     if (mockedResponses) {
       mockedResponses.forEach(mockedResponse => {
         this.addMockedResponse(mockedResponse);
@@ -122,12 +134,22 @@ ${unmatchedVars.map(d => `  ${stringifyForDisplay(d)}`).join('\n')}
       const timer = setTimeout(() => {
         if (configError) {
           try {
+            // The customErrorHandler function can return false to indicate that
+            // configError need not be passed to the onError function.
+            const shouldPassToOnError = typeof this.customErrorHandler !== 'function'
+              || this.customErrorHandler(configError, {
+                key,
+                mockedResponses,
+                operation,
+                unmatchedVars,
+              }) !== false;
+
             // The onError function can return false to indicate that
             // configError need not be passed to observer.error. For
             // example, the default implementation of onError calls
             // observer.error(configError) and then returns false to
             // prevent this extra (harmless) observer.error call.
-            if (this.onError(configError, observer) !== false) {
+            if (shouldPassToOnError && this.onError(configError, observer) !== false) {
               throw configError;
             }
           } catch (error) {
diff --git a/src/testing/react/MockedProvider.tsx b/src/testing/react/MockedProvider.tsx
index b64526411ff..2f022f73970 100644
--- a/src/testing/react/MockedProvider.tsx
+++ b/src/testing/react/MockedProvider.tsx
@@ -3,7 +3,7 @@ import * as React from 'react';
 import { ApolloClient, DefaultOptions } from '../../core';
 import { InMemoryCache as Cache } from '../../cache';
 import { ApolloProvider } from '../../react/context';
-import { MockLink, MockedResponse } from '../core';
+import { MockLink, MockLinkData, MockedResponse } from '../core';
 import { ApolloLink } from '../../link/core';
 import { Resolvers } from '../../core';
 import { ApolloCache } from '../../cache';
@@ -17,6 +17,7 @@ export interface MockedProviderProps<TSerializedCache = {}> {
   childProps?: object;
   children?: any;
   link?: ApolloLink;
+  onError?: (error: Error, mockLinkData: MockLinkData) => Boolean;
 }
 
 export interface MockedProviderState {
@@ -40,7 +41,8 @@ export class MockedProvider extends React.Component<
       defaultOptions,
       cache,
       resolvers,
-      link
+      link,
+      onError,
     } = this.props;
     const client = new ApolloClient({
       cache: cache || new Cache({ addTypename }),
@@ -48,6 +50,7 @@ export class MockedProvider extends React.Component<
       link: link || new MockLink(
         mocks || [],
         addTypename,
+        onError,
       ),
       resolvers,
     });