diff --git a/packages/eslint-plugin/src/rules/no-for-in-array.ts b/packages/eslint-plugin/src/rules/no-for-in-array.ts
index ec8ebe9125fb..45986948abe8 100644
--- a/packages/eslint-plugin/src/rules/no-for-in-array.ts
+++ b/packages/eslint-plugin/src/rules/no-for-in-array.ts
@@ -1,10 +1,10 @@
+import * as tsutils from 'ts-api-utils';
 import * as ts from 'typescript';
 
 import {
   createRule,
   getConstrainedTypeAtLocation,
   getParserServices,
-  isTypeArrayTypeOrUnionOfArrayTypes,
 } from '../util';
 import { getForStatementHeadLoc } from '../util/getForStatementHeadLoc';
 
@@ -32,10 +32,7 @@ export default createRule({
 
         const type = getConstrainedTypeAtLocation(services, node.right);
 
-        if (
-          isTypeArrayTypeOrUnionOfArrayTypes(type, checker) ||
-          (type.flags & ts.TypeFlags.StringLike) !== 0
-        ) {
+        if (isArrayLike(checker, type)) {
           context.report({
             loc: getForStatementHeadLoc(context.sourceCode, node),
             messageId: 'forInViolation',
@@ -45,3 +42,34 @@ export default createRule({
     };
   },
 });
+
+function isArrayLike(checker: ts.TypeChecker, type: ts.Type): boolean {
+  return isTypeRecurser(
+    type,
+    t => t.getNumberIndexType() != null && hasArrayishLength(checker, t),
+  );
+}
+
+function hasArrayishLength(checker: ts.TypeChecker, type: ts.Type): boolean {
+  const lengthProperty = type.getProperty('length');
+
+  if (lengthProperty == null) {
+    return false;
+  }
+
+  return tsutils.isTypeFlagSet(
+    checker.getTypeOfSymbol(lengthProperty),
+    ts.TypeFlags.NumberLike,
+  );
+}
+
+function isTypeRecurser(
+  type: ts.Type,
+  predicate: (t: ts.Type) => boolean,
+): boolean {
+  if (type.isUnionOrIntersection()) {
+    return type.types.some(t => isTypeRecurser(t, predicate));
+  }
+
+  return predicate(type);
+}
diff --git a/packages/eslint-plugin/tests/fixtures/tsconfig.lib-dom.json b/packages/eslint-plugin/tests/fixtures/tsconfig.lib-dom.json
new file mode 100644
index 000000000000..56c8433f6094
--- /dev/null
+++ b/packages/eslint-plugin/tests/fixtures/tsconfig.lib-dom.json
@@ -0,0 +1,6 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "lib": ["es2015", "es2017", "esnext", "dom"]
+  }
+}
diff --git a/packages/eslint-plugin/tests/rules/no-for-in-array.test.ts b/packages/eslint-plugin/tests/rules/no-for-in-array.test.ts
index 47b3d1ab3ea2..7721006b1d75 100644
--- a/packages/eslint-plugin/tests/rules/no-for-in-array.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-for-in-array.test.ts
@@ -23,6 +23,23 @@ for (const x of [3, 4, 5]) {
     `
 for (const x in { a: 1, b: 2, c: 3 }) {
   console.log(x);
+}
+    `,
+    // this is normally a type error, this test is here to make sure the rule
+    // doesn't include an "extra" report for it
+    `
+declare const nullish: null | undefined;
+// @ts-expect-error
+for (const k in nullish) {
+}
+    `,
+    `
+declare const obj: {
+  [key: number]: number;
+};
+
+for (const key in obj) {
+  console.log(key);
 }
     `,
   ],
@@ -177,5 +194,260 @@ for (const x
         },
       ],
     },
+    {
+      code: `
+declare const array: string[] | null;
+
+for (const key in array) {
+  console.log(key);
+}
+      `,
+      errors: [
+        {
+          column: 1,
+          endColumn: 25,
+          endLine: 4,
+          line: 4,
+          messageId: 'forInViolation',
+        },
+      ],
+    },
+    {
+      code: `
+declare const array: number[] | undefined;
+
+for (const key in array) {
+  console.log(key);
+}
+      `,
+      errors: [
+        {
+          column: 1,
+          endColumn: 25,
+          endLine: 4,
+          line: 4,
+          messageId: 'forInViolation',
+        },
+      ],
+    },
+    {
+      code: `
+declare const array: boolean[] | { a: 1; b: 2; c: 3 };
+
+for (const key in array) {
+  console.log(key);
+}
+      `,
+      errors: [
+        {
+          column: 1,
+          endColumn: 25,
+          endLine: 4,
+          line: 4,
+          messageId: 'forInViolation',
+        },
+      ],
+    },
+    {
+      code: `
+declare const array: [number, string];
+
+for (const key in array) {
+  console.log(key);
+}
+      `,
+      errors: [
+        {
+          column: 1,
+          endColumn: 25,
+          endLine: 4,
+          line: 4,
+          messageId: 'forInViolation',
+        },
+      ],
+    },
+    {
+      code: `
+declare const array: [number, string] | { a: 1; b: 2; c: 3 };
+
+for (const key in array) {
+  console.log(key);
+}
+      `,
+      errors: [
+        {
+          column: 1,
+          endColumn: 25,
+          endLine: 4,
+          line: 4,
+          messageId: 'forInViolation',
+        },
+      ],
+    },
+    {
+      code: `
+declare const array: string[] | Record<number, string>;
+
+for (const key in array) {
+  console.log(key);
+}
+      `,
+      errors: [
+        {
+          column: 1,
+          endColumn: 25,
+          endLine: 4,
+          line: 4,
+          messageId: 'forInViolation',
+        },
+      ],
+    },
+    {
+      code: `
+const arrayLike = /fe/.exec('foo');
+
+for (const x in arrayLike) {
+  console.log(x);
+}
+      `,
+      errors: [
+        {
+          column: 1,
+          endColumn: 27,
+          endLine: 4,
+          line: 4,
+          messageId: 'forInViolation',
+        },
+      ],
+    },
+    {
+      code: `
+declare const arrayLike: HTMLCollection;
+
+for (const x in arrayLike) {
+  console.log(x);
+}
+      `,
+      errors: [
+        {
+          column: 1,
+          endColumn: 27,
+          endLine: 4,
+          line: 4,
+          messageId: 'forInViolation',
+        },
+      ],
+      languageOptions: {
+        parserOptions: {
+          project: './tsconfig.lib-dom.json',
+          projectService: false,
+          tsconfigRootDir: rootDir,
+        },
+      },
+    },
+    {
+      code: `
+declare const arrayLike: NodeList;
+
+for (const x in arrayLike) {
+  console.log(x);
+}
+      `,
+      errors: [
+        {
+          column: 1,
+          endColumn: 27,
+          endLine: 4,
+          line: 4,
+          messageId: 'forInViolation',
+        },
+      ],
+      languageOptions: {
+        parserOptions: {
+          project: './tsconfig.lib-dom.json',
+          projectService: false,
+          tsconfigRootDir: rootDir,
+        },
+      },
+    },
+    {
+      code: `
+function foo() {
+  for (const a in arguments) {
+    console.log(a);
+  }
+}
+      `,
+      errors: [
+        {
+          column: 3,
+          endColumn: 29,
+          endLine: 3,
+          line: 3,
+          messageId: 'forInViolation',
+        },
+      ],
+    },
+    {
+      code: `
+declare const array:
+  | (({ a: string } & string[]) | Record<string, boolean>)
+  | Record<number, string>;
+
+for (const key in array) {
+  console.log(key);
+}
+      `,
+      errors: [
+        {
+          column: 1,
+          endColumn: 25,
+          endLine: 6,
+          line: 6,
+          messageId: 'forInViolation',
+        },
+      ],
+    },
+    {
+      code: `
+declare const array:
+  | (({ a: string } & RegExpExecArray) | Record<string, boolean>)
+  | Record<number, string>;
+
+for (const key in array) {
+  console.log(k);
+}
+      `,
+      errors: [
+        {
+          column: 1,
+          endColumn: 25,
+          endLine: 6,
+          line: 6,
+          messageId: 'forInViolation',
+        },
+      ],
+    },
+    {
+      code: `
+declare const obj: {
+  [key: number]: number;
+  length: 1;
+};
+
+for (const key in obj) {
+  console.log(key);
+}
+      `,
+      errors: [
+        {
+          column: 1,
+          endColumn: 23,
+          endLine: 7,
+          line: 7,
+          messageId: 'forInViolation',
+        },
+      ],
+    },
   ],
 });