diff --git a/source/rules/no-assign-mutated-array.ts b/source/rules/no-assign-mutated-array.ts
index 7edbadd..7f0ea19 100644
--- a/source/rules/no-assign-mutated-array.ts
+++ b/source/rules/no-assign-mutated-array.ts
@@ -17,7 +17,8 @@ import {
 import { ruleCreator } from "../utils";
 
 const mutatorRegExp = /^(fill|reverse|sort)$/;
-const creatorRegExp = /^(concat|entries|filter|keys|map|slice|splice|values)$/;
+const creatorRegExp =
+  /^(concat|entries|filter|keys|map|slice|splice|values|flat|flatMap)$/;
 
 const rule = ruleCreator({
   defaultOptions: [],
diff --git a/tests/rules/no-assign-mutated-array.ts b/tests/rules/no-assign-mutated-array.ts
index 0bc438c..a71a554 100644
--- a/tests/rules/no-assign-mutated-array.ts
+++ b/tests/rules/no-assign-mutated-array.ts
@@ -144,6 +144,24 @@ ruleTester({ types: true }).run("no-assign-mutated-array", rule, {
         );
       `,
     },
+    {
+      code: stripIndent`
+      // flat & mutated variable assignment
+      const a = [[0, 1], [2, 3]];
+      const b = a.flat().fill(0);
+      const c = a.flat().reverse();
+      const d = a.flat().sort();
+      `,
+    },
+    {
+      code: stripIndent`
+      // flatMap & mutated variable assignment
+      const a = [[0, 1], [2, 3]];
+      const b = a.flatMap(e => e).fill(0);
+      const c = a.flatMap(e => e).reverse();
+      const d = a.flatMap(e => e).sort();
+      `,
+    },
     {
       code: stripIndent`
         // https://github.com/cartant/eslint-plugin-etc/issues/27