diff --git a/packages/eslint-plugin/README.md b/packages/eslint-plugin/README.md
index 0428cff43fc..c4507267c6f 100644
--- a/packages/eslint-plugin/README.md
+++ b/packages/eslint-plugin/README.md
@@ -183,6 +183,7 @@ In these cases, we create what we call an extension rule; a rule within our plug
 | [`@typescript-eslint/default-param-last`](./docs/rules/default-param-last.md)                   | Enforce default parameters to be last                                          |                    |          |                   |
 | [`@typescript-eslint/func-call-spacing`](./docs/rules/func-call-spacing.md)                     | Require or disallow spacing between function identifiers and their invocations |                    | :wrench: |                   |
 | [`@typescript-eslint/indent`](./docs/rules/indent.md)                                           | Enforce consistent indentation                                                 |                    | :wrench: |                   |
+| [`@typescript-eslint/init-declarations`](./docs/rules/init-declarations.md)                     | require or disallow initialization in variable declarations                    |                    |          |                   |
 | [`@typescript-eslint/keyword-spacing`](./docs/rules/keyword-spacing.md)                         | Enforce consistent spacing before and after keywords                           |                    | :wrench: |                   |
 | [`@typescript-eslint/no-array-constructor`](./docs/rules/no-array-constructor.md)               | Disallow generic `Array` constructors                                          | :heavy_check_mark: | :wrench: |                   |
 | [`@typescript-eslint/no-dupe-class-members`](./docs/rules/no-dupe-class-members.md)             | Disallow duplicate class members                                               |                    |          |                   |
diff --git a/packages/eslint-plugin/docs/rules/init-declarations.md b/packages/eslint-plugin/docs/rules/init-declarations.md
new file mode 100644
index 00000000000..8888e2efef2
--- /dev/null
+++ b/packages/eslint-plugin/docs/rules/init-declarations.md
@@ -0,0 +1,22 @@
+# require or disallow initialization in variable declarations (`init-declarations`)
+
+## Rule Details
+
+This rule extends the base [`eslint/init-declarations`](https://eslint.org/docs/rules/init-declarations) rule.
+It adds support for TypeScript's `declare` variables.
+
+## How to use
+
+```cjson
+{
+  // note you must disable the base rule as it can report incorrect errors
+  "init-declarations": "off",
+  "@typescript-eslint/init-declarations": ["error"]
+}
+```
+
+## Options
+
+See [`eslint/init-declarations` options](https://eslint.org/docs/rules/init-declarations#options).
+
+<sup>Taken with ❤️ [from ESLint core](https://github.com/eslint/eslint/blob/master/docs/rules/init-declarations.md)</sup>
diff --git a/packages/eslint-plugin/src/configs/all.json b/packages/eslint-plugin/src/configs/all.json
index ec65f143c59..99e6060d670 100644
--- a/packages/eslint-plugin/src/configs/all.json
+++ b/packages/eslint-plugin/src/configs/all.json
@@ -22,6 +22,8 @@
     "@typescript-eslint/func-call-spacing": "error",
     "indent": "off",
     "@typescript-eslint/indent": "error",
+    "init-declarations": "off",
+    "@typescript-eslint/init-declarations": "error",
     "keyword-spacing": "off",
     "@typescript-eslint/keyword-spacing": "error",
     "@typescript-eslint/member-delimiter-style": "error",
diff --git a/packages/eslint-plugin/src/rules/index.ts b/packages/eslint-plugin/src/rules/index.ts
index 63c402297e3..cbc3b8c68f9 100644
--- a/packages/eslint-plugin/src/rules/index.ts
+++ b/packages/eslint-plugin/src/rules/index.ts
@@ -87,6 +87,7 @@ import requireAwait from './require-await';
 import restrictPlusOperands from './restrict-plus-operands';
 import restrictTemplateExpressions from './restrict-template-expressions';
 import returnAwait from './return-await';
+import initDeclarations from './init-declarations';
 import semi from './semi';
 import spaceBeforeFunctionParen from './space-before-function-paren';
 import strictBooleanExpressions from './strict-boolean-expressions';
@@ -118,6 +119,7 @@ export default {
   'func-call-spacing': funcCallSpacing,
   'generic-type-naming': genericTypeNaming,
   indent: indent,
+  'init-declarations': initDeclarations,
   'interface-name-prefix': interfaceNamePrefix,
   'keyword-spacing': keywordSpacing,
   'member-delimiter-style': memberDelimiterStyle,
diff --git a/packages/eslint-plugin/src/rules/init-declarations.ts b/packages/eslint-plugin/src/rules/init-declarations.ts
new file mode 100644
index 00000000000..b4368527e0c
--- /dev/null
+++ b/packages/eslint-plugin/src/rules/init-declarations.ts
@@ -0,0 +1,53 @@
+import {
+  TSESTree,
+  AST_NODE_TYPES,
+} from '@typescript-eslint/experimental-utils';
+import baseRule from 'eslint/lib/rules/init-declarations';
+import {
+  InferOptionsTypeFromRule,
+  InferMessageIdsTypeFromRule,
+  createRule,
+} from '../util';
+
+export type Options = InferOptionsTypeFromRule<typeof baseRule>;
+export type MessageIds = InferMessageIdsTypeFromRule<typeof baseRule>;
+
+export default createRule<Options, MessageIds>({
+  name: 'init-declarations',
+  meta: {
+    type: 'suggestion',
+    docs: {
+      description:
+        'require or disallow initialization in variable declarations',
+      category: 'Variables',
+      recommended: false,
+      extendsBaseRule: true,
+    },
+    schema: baseRule.meta.schema,
+    messages: baseRule.meta.messages,
+  },
+  defaultOptions: ['always'],
+  create(context) {
+    const rules = baseRule.create(context);
+    const mode = context.options[0] || 'always';
+
+    return {
+      'VariableDeclaration:exit'(node: TSESTree.VariableDeclaration): void {
+        if (mode === 'always') {
+          if (node.declare) {
+            return;
+          }
+          if (
+            node.parent?.type === AST_NODE_TYPES.TSModuleBlock &&
+            node.parent.parent?.type === AST_NODE_TYPES.TSModuleDeclaration &&
+            node.parent.parent?.declare
+          ) {
+            return;
+          }
+        }
+
+        rules['VariableDeclaration:exit'](node);
+      },
+    };
+  },
+});
diff --git a/packages/eslint-plugin/tests/rules/init-declarations.test.ts b/packages/eslint-plugin/tests/rules/init-declarations.test.ts
new file mode 100644
index 00000000000..6f4c8f75ebb
--- /dev/null
+++ b/packages/eslint-plugin/tests/rules/init-declarations.test.ts
@@ -0,0 +1,728 @@
+import { AST_NODE_TYPES } from '@typescript-eslint/experimental-utils';
+import rule from '../../src/rules/init-declarations';
+import { RuleTester } from '../RuleTester';
+
+const ruleTester = new RuleTester({
+  parser: '@typescript-eslint/parser',
+});
+
+ruleTester.run('init-declarations', rule, {
+  valid: [
+    // checking compatibility with base rule
+    'var foo = null;',
+    'foo = true;',
+    `
+var foo = 1,
+  bar = false,
+  baz = {};
+    `,
+    `
+function foo() {
+  var foo = 0;
+  var bar = [];
+}
+    `,
+    'var fn = function() {};',
+    'var foo = (bar = 2);',
+    'for (var i = 0; i < 1; i++) {}',
+    `
+for (var foo in []) {
+}
+    `,
+    {
+      code: `
+for (var foo of []) {
+}
+      `,
+      parserOptions: { ecmaVersion: 6 },
+    },
+    {
+      code: 'let a = true;',
+      options: ['always'],
+      parserOptions: { ecmaVersion: 6 },
+    },
+    {
+      code: 'const a = {};',
+      options: ['always'],
+      parserOptions: { ecmaVersion: 6 },
+    },
+    {
+      code: `
+function foo() {
+  let a = 1,
+    b = false;
+  if (a) {
+    let c = 3,
+      d = null;
+  }
+}
+      `,
+      options: ['always'],
+      parserOptions: { ecmaVersion: 6 },
+    },
+    {
+      code: `
+function foo() {
+  const a = 1,
+    b = true;
+  if (a) {
+    const c = 3,
+      d = null;
+  }
+}
+      `,
+      options: ['always'],
+      parserOptions: { ecmaVersion: 6 },
+    },
+    {
+      code: `
+function foo() {
+  let a = 1;
+  const b = false;
+  var c = true;
+}
+      `,
+      options: ['always'],
+      parserOptions: { ecmaVersion: 6 },
+    },
+    {
+      code: 'var foo;',
+      options: ['never'],
+      parserOptions: { ecmaVersion: 6 },
+    },
+    {
+      code: 'var foo, bar, baz;',
+      options: ['never'],
+      parserOptions: { ecmaVersion: 6 },
+    },
+    {
+      code: `
+function foo() {
+  var foo;
+  var bar;
+}
+      `,
+      options: ['never'],
+      parserOptions: { ecmaVersion: 6 },
+    },
+    {
+      code: 'let a;',
+      options: ['never'],
+      parserOptions: { ecmaVersion: 6 },
+    },
+    {
+      code: 'const a = 1;',
+      options: ['never'],
+      parserOptions: { ecmaVersion: 6 },
+    },
+    {
+      code: `
+function foo() {
+  let a, b;
+  if (a) {
+    let c, d;
+  }
+}
+      `,
+      options: ['never'],
+      parserOptions: { ecmaVersion: 6 },
+    },
+    {
+      code: `
+function foo() {
+  const a = 1,
+    b = true;
+  if (a) {
+    const c = 3,
+      d = null;
+  }
+}
+      `,
+      options: ['never'],
+      parserOptions: { ecmaVersion: 6 },
+    },
+    {
+      code: `
+function foo() {
+  let a;
+  const b = false;
+  var c;
+}
+      `,
+      options: ['never'],
+      parserOptions: { ecmaVersion: 6 },
+    },
+    {
+      code: 'for (var i = 0; i < 1; i++) {}',
+      options: ['never', { ignoreForLoopInit: true }],
+    },
+    {
+      code: `
+for (var foo in []) {
+}
+      `,
+      options: ['never', { ignoreForLoopInit: true }],
+    },
+    {
+      code: `
+for (var foo of []) {
+}
+      `,
+      options: ['never', { ignoreForLoopInit: true }],
+      parserOptions: { ecmaVersion: 6 },
+    },
+    {
+      code: `
+function foo() {
+  var bar = 1;
+  let baz = 2;
+  const qux = 3;
+}
+      `,
+      options: ['always'],
+    },
+
+    // typescript-eslint
+    {
+      code: 'declare const foo: number;',
+      options: ['always'],
+    },
+    {
+      code: 'declare const foo: number;',
+      options: ['never'],
+    },
+    {
+      code: `
+declare namespace myLib {
+  let numberOfGreetings: number;
+}
+      `,
+      options: ['always'],
+    },
+    {
+      code: `
+declare namespace myLib {
+  let numberOfGreetings: number;
+}
+      `,
+      options: ['never'],
+    },
+    {
+      code: `
+interface GreetingSettings {
+  greeting: string;
+  duration?: number;
+  color?: string;
+}
+      `,
+    },
+    {
+      code: `
+interface GreetingSettings {
+  greeting: string;
+  duration?: number;
+  color?: string;
+}
+      `,
+      options: ['never'],
+    },
+    'type GreetingLike = string | (() => string) | Greeter;',
+    {
+      code: 'type GreetingLike = string | (() => string) | Greeter;',
+      options: ['never'],
+    },
+    {
+      code: `
+function foo() {
+  var bar: string;
+}
+      `,
+      options: ['never'],
+    },
+    {
+      code: 'var bar: string;',
+      options: ['never'],
+    },
+    {
+      code: `
+var bar: string = function(): string {
+  return 'string';
+};
+      `,
+      options: ['always'],
+    },
+    {
+      code: `
+var bar: string = function(arg1: stirng): string {
+  return 'string';
+};
+      `,
+      options: ['always'],
+    },
+    {
+      code: "function foo(arg1: string = 'string'): void {}",
+      options: ['never'],
+    },
+    {
+      code: "const foo: string = 'hello';",
+      options: ['never'],
+    },
+    {
+      code: `
+const class1 = class NAME {
+  constructor() {
+    var name1: string = 'hello';
+  }
+};
+      `,
+    },
+    {
+      code: `
+const class1 = class NAME {
+  static pi: number = 3.14;
+};
+      `,
+    },
+    {
+      code: `
+const class1 = class NAME {
+  static pi: number = 3.14;
+};
+      `,
+      options: ['never'],
+    },
+    {
+      code: `
+interface IEmployee {
+  empCode: number;
+  empName: string;
+  getSalary: (number) => number; // arrow function
+  getManagerName(number): string;
+}
+      `,
+    },
+    {
+      code: `
+interface IEmployee {
+  empCode: number;
+  empName: string;
+  getSalary: (number) => number; // arrow function
+  getManagerName(number): string;
+}
+      `,
+      options: ['never'],
+    },
+    {
+      code: "declare const foo: number = 'asd';",
+      options: ['always'],
+    },
+
+    {
+      code: "const foo: number = 'asd';",
+      options: ['always'],
+    },
+    {
+      code: 'const foo: number;',
+      options: ['never'],
+    },
+    {
+      code: `
+namespace myLib {
+  let numberOfGreetings: number;
+}
+      `,
+      options: ['never'],
+    },
+    {
+      code: `
+namespace myLib {
+  let numberOfGreetings: number = 2;
+}
+      `,
+      options: ['always'],
+    },
+  ],
+  invalid: [
+    // checking compatibility with base rule
+    {
+      code: 'var foo;',
+      options: ['always'],
+      errors: [
+        {
+          messageId: 'initialized',
+          data: { idName: 'foo' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: 'for (var a in []) var foo;',
+      options: ['always'],
+      errors: [
+        {
+          messageId: 'initialized',
+          data: { idName: 'foo' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: `
+var foo,
+  bar = false,
+  baz;
+      `,
+      options: ['always'],
+      errors: [
+        {
+          messageId: 'initialized',
+          data: { idName: 'foo' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+        {
+          messageId: 'initialized',
+          data: { idName: 'baz' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: `
+function foo() {
+  var foo = 0;
+  var bar;
+}
+      `,
+      options: ['always'],
+      errors: [
+        {
+          messageId: 'initialized',
+          data: { idName: 'bar' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: `
+function foo() {
+  var foo;
+  var bar = foo;
+}
+      `,
+      options: ['always'],
+      errors: [
+        {
+          messageId: 'initialized',
+          data: { idName: 'foo' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: 'let a;',
+      options: ['always'],
+      errors: [
+        {
+          messageId: 'initialized',
+          data: { idName: 'a' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: `
+function foo() {
+  let a = 1,
+    b;
+  if (a) {
+    let c = 3,
+      d = null;
+  }
+}
+      `,
+      options: ['always'],
+      errors: [
+        {
+          messageId: 'initialized',
+          data: { idName: 'b' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: `
+function foo() {
+  let a;
+  const b = false;
+  var c;
+}
+      `,
+      options: ['always'],
+      errors: [
+        {
+          messageId: 'initialized',
+          data: { idName: 'a' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+        {
+          messageId: 'initialized',
+          data: { idName: 'c' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: 'var foo = (bar = 2);',
+      options: ['never'],
+      errors: [
+        {
+          messageId: 'notInitialized',
+          data: { idName: 'foo' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: 'var foo = true;',
+      options: ['never'],
+      errors: [
+        {
+          messageId: 'notInitialized',
+          data: { idName: 'foo' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: `
+var foo,
+  bar = 5,
+  baz = 3;
+      `,
+      options: ['never'],
+      errors: [
+        {
+          messageId: 'notInitialized',
+          data: { idName: 'bar' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+        {
+          messageId: 'notInitialized',
+          data: { idName: 'baz' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: `
+function foo() {
+  var foo;
+  var bar = foo;
+}
+      `,
+      options: ['never'],
+      errors: [
+        {
+          messageId: 'notInitialized',
+          data: { idName: 'bar' },
+
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: 'let a = 1;',
+      options: ['never'],
+      errors: [
+        {
+          messageId: 'notInitialized',
+          data: { idName: 'a' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: `
+function foo() {
+  let a = 'foo',
+    b;
+  if (a) {
+    let c, d;
+  }
+}
+      `,
+      options: ['never'],
+      errors: [
+        {
+          messageId: 'notInitialized',
+          data: { idName: 'a' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: `
+function foo() {
+  let a;
+  const b = false;
+  var c = 1;
+}
+      `,
+      options: ['never'],
+      errors: [
+        {
+          messageId: 'notInitialized',
+          data: { idName: 'c' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: 'for (var i = 0; i < 1; i++) {}',
+      options: ['never'],
+      errors: [
+        {
+          messageId: 'notInitialized',
+          data: { idName: 'i' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: `
+for (var foo in []) {
+}
+      `,
+      options: ['never'],
+      errors: [
+        {
+          messageId: 'notInitialized',
+          data: { idName: 'foo' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: `
+for (var foo of []) {
+}
+      `,
+      options: ['never'],
+      errors: [
+        {
+          messageId: 'notInitialized',
+          data: { idName: 'foo' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: `
+function foo() {
+  var bar;
+}
+      `,
+      options: ['always'],
+      errors: [
+        {
+          messageId: 'initialized',
+          data: { idName: 'bar' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+
+    // typescript-eslint
+    {
+      code: "let arr: string[] = ['arr', 'ar'];",
+      options: ['never'],
+      errors: [
+        {
+          messageId: 'notInitialized',
+          data: { idName: 'arr' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: 'let arr: string = function() {};',
+      options: ['never'],
+      errors: [
+        {
+          messageId: 'notInitialized',
+          data: { idName: 'arr' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: `
+const class1 = class NAME {
+  constructor() {
+    var name1: string = 'hello';
+  }
+};
+      `,
+      options: ['never'],
+      errors: [
+        {
+          messageId: 'notInitialized',
+          data: { idName: 'name1' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: 'let arr: string;',
+      options: ['always'],
+      errors: [
+        {
+          messageId: 'initialized',
+          data: { idName: 'arr' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: "declare var foo: number = 'asd';",
+      options: ['never'],
+      errors: [
+        {
+          messageId: 'notInitialized',
+          data: { idName: 'foo' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: `
+namespace myLib {
+  let numberOfGreetings: number;
+}
+      `,
+      options: ['always'],
+      errors: [
+        {
+          messageId: 'initialized',
+          data: { idName: 'numberOfGreetings' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+    {
+      code: `
+namespace myLib {
+  let numberOfGreetings: number = 2;
+}
+      `,
+      options: ['never'],
+      errors: [
+        {
+          messageId: 'notInitialized',
+          data: { idName: 'numberOfGreetings' },
+          type: AST_NODE_TYPES.VariableDeclarator,
+        },
+      ],
+    },
+  ],
+});
diff --git a/packages/eslint-plugin/typings/eslint-rules.d.ts b/packages/eslint-plugin/typings/eslint-rules.d.ts
index ac8700d42e5..eb2d1cd9c60 100644
--- a/packages/eslint-plugin/typings/eslint-rules.d.ts
+++ b/packages/eslint-plugin/typings/eslint-rules.d.ts
@@ -622,3 +622,21 @@ declare module 'eslint/lib/rules/no-extra-semi' {
   >;
   export = rule;
 }
+
+declare module 'eslint/lib/rules/init-declarations' {
+  import { TSESLint, TSESTree } from '@typescript-eslint/experimental-utils';
+
+  const rule: TSESLint.RuleModule<
+    'initialized' | 'notInitialized',
+    [
+      'always' | 'never',
+      {
+        ignoreForLoopInit?: boolean;
+      }?,
+    ],
+    {
+      'VariableDeclaration:exit'(node: TSESTree.VariableDeclaration): void;
+    }
+  >;
+  export = rule;
+}