diff --git a/packages/eslint-plugin/src/rules/no-unused-expressions.ts b/packages/eslint-plugin/src/rules/no-unused-expressions.ts
index f7d86f50c1c7..b2eb6f8e30b7 100644
--- a/packages/eslint-plugin/src/rules/no-unused-expressions.ts
+++ b/packages/eslint-plugin/src/rules/no-unused-expressions.ts
@@ -12,10 +12,7 @@ export default util.createRule({
       recommended: false,
     },
     schema: baseRule.meta.schema,
-    messages: {
-      expected:
-        'Expected an assignment or function call and instead saw an expression.',
-    },
+    messages: {},
   },
   defaultOptions: [],
   create(context) {
@@ -23,9 +20,13 @@ export default util.createRule({
 
     return {
       ExpressionStatement(node): void {
-        if (node.expression.type === AST_NODE_TYPES.OptionalCallExpression) {
+        if (
+          node.directive ||
+          node.expression.type === AST_NODE_TYPES.OptionalCallExpression
+        ) {
           return;
         }
+
         rules.ExpressionStatement(node);
       },
     };
diff --git a/packages/eslint-plugin/tests/rules/no-unused-expressions.test.ts b/packages/eslint-plugin/tests/rules/no-unused-expressions.test.ts
index 46653b30c663..feb3a584bcc3 100644
--- a/packages/eslint-plugin/tests/rules/no-unused-expressions.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-unused-expressions.test.ts
@@ -1,3 +1,4 @@
+import { TSESLint } from '@typescript-eslint/experimental-utils';
 import rule from '../../src/rules/no-unused-expressions';
 import { RuleTester } from '../RuleTester';
 
@@ -10,9 +11,11 @@ const ruleTester = new RuleTester({
   parser: '@typescript-eslint/parser',
 });
 
+type TestCaseError = Omit<TSESLint.TestCaseError<string>, 'messageId'>;
+
 // the base rule doesn't have messageIds
 function error(
-  messages: { line: number; column: number }[],
+  messages: TestCaseError[],
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
 ): any[] {
   return messages.map(message => ({
@@ -42,6 +45,26 @@ ruleTester.run('no-unused-expressions', rule, {
     `
       a?.['b']?.c();
     `,
+    `
+      module Foo {
+        'use strict';
+      }
+    `,
+    `
+      namespace Foo {
+        'use strict';
+
+        export class Foo {}
+        export class Bar {}
+      }
+    `,
+    `
+      function foo() {
+        'use strict';
+
+        return null;
+      }
+    `,
   ],
   invalid: [
     {
@@ -176,5 +199,56 @@ one.two?.three.four;
         },
       ]),
     },
+    {
+      code: `
+module Foo {
+  const foo = true;
+  'use strict';
+}
+      `,
+      errors: error([
+        {
+          line: 4,
+          endLine: 4,
+          column: 3,
+          endColumn: 16,
+        },
+      ]),
+    },
+    {
+      code: `
+namespace Foo {
+  export class Foo {}
+  export class Bar {}
+
+  'use strict';
+}
+      `,
+      errors: error([
+        {
+          line: 6,
+          endLine: 6,
+          column: 3,
+          endColumn: 16,
+        },
+      ]),
+    },
+    {
+      code: `
+function foo() {
+  const foo = true;
+
+  'use strict';
+}
+      `,
+      errors: error([
+        {
+          line: 5,
+          endLine: 5,
+          column: 3,
+          endColumn: 16,
+        },
+      ]),
+    },
   ],
 });
diff --git a/packages/typescript-estree/src/ts-estree/ts-estree.ts b/packages/typescript-estree/src/ts-estree/ts-estree.ts
index afda76ead68d..1e473854029b 100644
--- a/packages/typescript-estree/src/ts-estree/ts-estree.ts
+++ b/packages/typescript-estree/src/ts-estree/ts-estree.ts
@@ -691,6 +691,7 @@ export interface ExportSpecifier extends BaseNode {
 export interface ExpressionStatement extends BaseNode {
   type: AST_NODE_TYPES.ExpressionStatement;
   expression: Expression;
+  directive?: string;
 }
 
 export interface ForInStatement extends BaseNode {