diff --git a/CHANGELOG.md b/CHANGELOG.md
index fef44a6a3939..7b67389a430c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -30,6 +30,7 @@
 
 ### Fixes
 
+- `[expect]` Standardize file naming in `expect` ([#7306](https://github.com/facebook/jest/pull/7306))
 - `[jest-each]` Add empty array validation check ([#7249](https://github.com/facebook/jest/pull/7249))
 - `[jest-cli]` Interrupt tests if interactive watch plugin key is pressed ([#7222](https://github.com/facebook/jest/pull/7222))
 - `[jest-cli]` Fix coverage summary reporting ([#7058](https://github.com/facebook/jest/pull/7058))
diff --git a/packages/expect/src/__tests__/__snapshots__/spy_matchers.test.js.snap b/packages/expect/src/__tests__/__snapshots__/spyMatchers.test.js.snap
similarity index 100%
rename from packages/expect/src/__tests__/__snapshots__/spy_matchers.test.js.snap
rename to packages/expect/src/__tests__/__snapshots__/spyMatchers.test.js.snap
diff --git a/packages/expect/src/__tests__/__snapshots__/to_throw_matchers.test.js.snap b/packages/expect/src/__tests__/__snapshots__/toThrowMatchers.test.js.snap
similarity index 100%
rename from packages/expect/src/__tests__/__snapshots__/to_throw_matchers.test.js.snap
rename to packages/expect/src/__tests__/__snapshots__/toThrowMatchers.test.js.snap
diff --git a/packages/expect/src/__tests__/assertion_counts.test.js b/packages/expect/src/__tests__/assertionCounts.test.js
similarity index 100%
rename from packages/expect/src/__tests__/assertion_counts.test.js
rename to packages/expect/src/__tests__/assertionCounts.test.js
diff --git a/packages/expect/src/__tests__/asymmetric_matchers.test.js b/packages/expect/src/__tests__/asymmetricMatchers.test.js
similarity index 99%
rename from packages/expect/src/__tests__/asymmetric_matchers.test.js
rename to packages/expect/src/__tests__/asymmetricMatchers.test.js
index 9b7a030d4d54..08b0907d09ee 100644
--- a/packages/expect/src/__tests__/asymmetric_matchers.test.js
+++ b/packages/expect/src/__tests__/asymmetricMatchers.test.js
@@ -20,7 +20,7 @@ const {
   stringNotContaining,
   stringMatching,
   stringNotMatching,
-} = require('../asymmetric_matchers');
+} = require('../asymmetricMatchers');
 
 test('Any.asymmetricMatch()', () => {
   const Thing = function() {};
diff --git a/packages/expect/src/__tests__/extend.test.js b/packages/expect/src/__tests__/extend.test.js
index 8fe6b6f3c78e..e2f3ecf0bdd6 100644
--- a/packages/expect/src/__tests__/extend.test.js
+++ b/packages/expect/src/__tests__/extend.test.js
@@ -8,7 +8,7 @@
 
 const matcherUtils = require('jest-matcher-utils');
 const {iterableEquality, subsetEquality} = require('../utils');
-const {equals} = require('../jasmine_utils');
+const {equals} = require('../jasmineUtils');
 const jestExpect = require('../');
 
 jestExpect.extend({
diff --git a/packages/expect/src/__tests__/fake_chalk.test.js b/packages/expect/src/__tests__/fakeChalk.test.js
similarity index 88%
rename from packages/expect/src/__tests__/fake_chalk.test.js
rename to packages/expect/src/__tests__/fakeChalk.test.js
index c461b75c1b2d..532dae6144c7 100644
--- a/packages/expect/src/__tests__/fake_chalk.test.js
+++ b/packages/expect/src/__tests__/fakeChalk.test.js
@@ -6,7 +6,7 @@
  */
 'use strict';
 
-const fakeChalk = jest.requireActual('../fake_chalk');
+const fakeChalk = jest.requireActual('../fakeChalk');
 
 describe('Fake Chalk', () => {
   it('returns input when invoked', () => {
diff --git a/packages/expect/src/__tests__/is_error.test.js b/packages/expect/src/__tests__/isError.test.js
similarity index 100%
rename from packages/expect/src/__tests__/is_error.test.js
rename to packages/expect/src/__tests__/isError.test.js
diff --git a/packages/expect/src/__tests__/spy_matchers.test.js b/packages/expect/src/__tests__/spyMatchers.test.js
similarity index 100%
rename from packages/expect/src/__tests__/spy_matchers.test.js
rename to packages/expect/src/__tests__/spyMatchers.test.js
diff --git a/packages/expect/src/__tests__/symbol_in_objects.test.js b/packages/expect/src/__tests__/symbolInObjects.test.js
similarity index 100%
rename from packages/expect/src/__tests__/symbol_in_objects.test.js
rename to packages/expect/src/__tests__/symbolInObjects.test.js
diff --git a/packages/expect/src/__tests__/to_throw_matchers.test.js b/packages/expect/src/__tests__/toThrowMatchers.test.js
similarity index 100%
rename from packages/expect/src/__tests__/to_throw_matchers.test.js
rename to packages/expect/src/__tests__/toThrowMatchers.test.js
diff --git a/packages/expect/src/asymmetric_matchers.js b/packages/expect/src/asymmetricMatchers.js
similarity index 98%
rename from packages/expect/src/asymmetric_matchers.js
rename to packages/expect/src/asymmetricMatchers.js
index b182fb1f1c44..01cc89af8550 100644
--- a/packages/expect/src/asymmetric_matchers.js
+++ b/packages/expect/src/asymmetricMatchers.js
@@ -7,13 +7,7 @@
  * @flow
  */
 
-import {
-  equals,
-  fnNameFor,
-  hasProperty,
-  isA,
-  isUndefined,
-} from './jasmine_utils';
+import {equals, fnNameFor, hasProperty, isA, isUndefined} from './jasmineUtils';
 
 import {emptyObject} from './utils';
 
diff --git a/packages/expect/src/extract_expected_assertions_errors.js b/packages/expect/src/extractExpectedAssertionsErrors.js
similarity index 97%
rename from packages/expect/src/extract_expected_assertions_errors.js
rename to packages/expect/src/extractExpectedAssertionsErrors.js
index af7d243142ae..29f766e6d7f9 100644
--- a/packages/expect/src/extract_expected_assertions_errors.js
+++ b/packages/expect/src/extractExpectedAssertionsErrors.js
@@ -14,7 +14,7 @@ import {
   pluralize,
 } from 'jest-matcher-utils';
 
-import {getState, setState} from './jest_matchers_object';
+import {getState, setState} from './jestMatchersObject';
 
 const resetAssertionsLocalState = () => {
   setState({
diff --git a/packages/expect/src/fake_chalk.js b/packages/expect/src/fakeChalk.js
similarity index 100%
rename from packages/expect/src/fake_chalk.js
rename to packages/expect/src/fakeChalk.js
diff --git a/packages/expect/src/index.js b/packages/expect/src/index.js
index 573d1bf9b42c..4c0aef0d3e92 100644
--- a/packages/expect/src/index.js
+++ b/packages/expect/src/index.js
@@ -23,11 +23,11 @@ import type {
 import * as matcherUtils from 'jest-matcher-utils';
 import {iterableEquality, subsetEquality} from './utils';
 import matchers from './matchers';
-import spyMatchers from './spy_matchers';
+import spyMatchers from './spyMatchers';
 import toThrowMatchers, {
   createMatcher as createThrowMatcher,
-} from './to_throw_matchers';
-import {equals} from './jasmine_utils';
+} from './toThrowMatchers';
+import {equals} from './jasmineUtils';
 import {
   any,
   anything,
@@ -39,15 +39,15 @@ import {
   stringNotContaining,
   stringMatching,
   stringNotMatching,
-} from './asymmetric_matchers';
+} from './asymmetricMatchers';
 import {
   INTERNAL_MATCHER_FLAG,
   getState,
   setState,
   getMatchers,
   setMatchers,
-} from './jest_matchers_object';
-import extractExpectedAssertionsErrors from './extract_expected_assertions_errors';
+} from './jestMatchersObject';
+import extractExpectedAssertionsErrors from './extractExpectedAssertionsErrors';
 
 class JestAssertionError extends Error {
   matcherResult: any;
diff --git a/packages/expect/src/jasmine_utils.js b/packages/expect/src/jasmineUtils.js
similarity index 100%
rename from packages/expect/src/jasmine_utils.js
rename to packages/expect/src/jasmineUtils.js
diff --git a/packages/expect/src/jest_matchers_object.js b/packages/expect/src/jestMatchersObject.js
similarity index 97%
rename from packages/expect/src/jest_matchers_object.js
rename to packages/expect/src/jestMatchersObject.js
index 253681620fce..b3b7d8f87d7d 100644
--- a/packages/expect/src/jest_matchers_object.js
+++ b/packages/expect/src/jestMatchersObject.js
@@ -7,7 +7,7 @@
  * @flow
  */
 
-import {AsymmetricMatcher} from './asymmetric_matchers';
+import {AsymmetricMatcher} from './asymmetricMatchers';
 import type {
   Expect,
   MatchersObject,
diff --git a/packages/expect/src/matchers.js b/packages/expect/src/matchers.js
index 043032bc0803..4e9575213513 100644
--- a/packages/expect/src/matchers.js
+++ b/packages/expect/src/matchers.js
@@ -32,7 +32,7 @@ import {
   typeEquality,
   isOneline,
 } from './utils';
-import {equals} from './jasmine_utils';
+import {equals} from './jasmineUtils';
 
 type ContainIterable =
   | Array<any>
diff --git a/packages/expect/src/spy_matchers.js b/packages/expect/src/spyMatchers.js
similarity index 99%
rename from packages/expect/src/spy_matchers.js
rename to packages/expect/src/spyMatchers.js
index 2a176fb9e1f1..5571bd837c79 100644
--- a/packages/expect/src/spy_matchers.js
+++ b/packages/expect/src/spyMatchers.js
@@ -23,7 +23,7 @@ import {
   printWithType,
   RECEIVED_COLOR,
 } from 'jest-matcher-utils';
-import {equals} from './jasmine_utils';
+import {equals} from './jasmineUtils';
 import {iterableEquality, partition, isOneline} from './utils';
 import diff from 'jest-diff';
 
diff --git a/packages/expect/src/to_throw_matchers.js b/packages/expect/src/toThrowMatchers.js
similarity index 99%
rename from packages/expect/src/to_throw_matchers.js
rename to packages/expect/src/toThrowMatchers.js
index b5e953a10792..48f69b46d630 100644
--- a/packages/expect/src/to_throw_matchers.js
+++ b/packages/expect/src/toThrowMatchers.js
@@ -19,7 +19,7 @@ import {
   printExpected,
   printWithType,
 } from 'jest-matcher-utils';
-import {equals} from './jasmine_utils';
+import {equals} from './jasmineUtils';
 import {isError} from './utils';
 
 export const createMatcher = (matcherName: string, fromPromise?: boolean) => (
diff --git a/packages/expect/src/utils.js b/packages/expect/src/utils.js
index 9a7a0220fac5..2c7de7ab2237 100644
--- a/packages/expect/src/utils.js
+++ b/packages/expect/src/utils.js
@@ -12,7 +12,7 @@ import {
   isA,
   isImmutableUnorderedKeyed,
   isImmutableUnorderedSet,
-} from './jasmine_utils';
+} from './jasmineUtils';
 
 type GetPath = {
   hasEndProp?: boolean,
diff --git a/scripts/browserBuild.js b/scripts/browserBuild.js
index c7f0414c7aa5..ae1c5b3cc636 100644
--- a/scripts/browserBuild.js
+++ b/scripts/browserBuild.js
@@ -45,7 +45,7 @@ function browserBuild(pkgName, entryPath, destination) {
       {
         resolveId(id) {
           return id === 'chalk'
-            ? path.resolve(__dirname, '../packages/expect/build/fake_chalk.js')
+            ? path.resolve(__dirname, '../packages/expect/build/fakeChalk.js')
             : undefined;
         },
       },