diff --git a/changelog_unreleased/typescript/pr-7228.md b/changelog_unreleased/typescript/pr-7228.md
new file mode 100644
index 000000000..10139ec1c
--- /dev/null
+++ b/changelog_unreleased/typescript/pr-7228.md
@@ -0,0 +1,18 @@
+#### Fix edge cases of printing index signatures ([#7228](https://github.com/prettier/prettier/pull/7228) by [@cola119](https://github.com/cola119))
+
+Even though index signatures without type annotations or with multiple parameters aren't valid TypeScript, the TypeScript parser supports this syntax. In line with the [previous error recovery efforts](https://prettier.io/blog/2019/11/09/1.19.0.html#enable-formatting-even-if-there-are-parse-errors-in-some-cases-6816-by-thorn0-and-the-babel-team), Prettier now makes sure its output still can be parsed in these cases. Previous versions produced unparseable code.
+
+<!-- prettier-ignore -->
+```ts
+// Input
+type A = { [key: string] };
+type B = { [a: string, b: string]: string; };  
+
+// Prettier stable
+type A = { [key: string]:  };
+type B = { [a: stringb: string]: string };
+
+// Prettier master
+type A = { [key: string] };
+type B = { [a: string, b: string]: string };
+```
diff --git a/src/language-js/printer-estree.js b/src/language-js/printer-estree.js
index 29a4ab142..0f837cf3f 100644
--- a/src/language-js/printer-estree.js
+++ b/src/language-js/printer-estree.js
@@ -3241,15 +3241,28 @@ function printPathNoParens(path, options, print, args) {
     case "TSIndexSignature": {
       const parent = path.getParentNode();
 
+      const parametersGroup = group(
+        concat([
+          indent(
+            concat([
+              softline,
+              join(concat([", ", softline]), path.map(print, "parameters"))
+            ])
+          ),
+          ifBreak(shouldPrintComma(options) ? "," : ""),
+          softline
+        ])
+      );
+
       return concat([
         n.export ? "export " : "",
         n.accessibility ? concat([n.accessibility, " "]) : "",
         n.static ? "static " : "",
         n.readonly ? "readonly " : "",
         "[",
-        n.parameters ? concat(path.map(print, "parameters")) : "",
-        "]: ",
-        path.call(print, "typeAnnotation"),
+        n.parameters ? parametersGroup : "",
+        n.typeAnnotation ? "]: " : "]",
+        n.typeAnnotation ? path.call(print, "typeAnnotation") : "",
         parent.type === "ClassBody" ? semi : ""
       ]);
     }
diff --git a/tests/typescript_error_recovery/__snapshots__/jsfmt.spec.js.snap b/tests/typescript_error_recovery/__snapshots__/jsfmt.spec.js.snap
index 09f0493bb..5ad364911 100644
--- a/tests/typescript_error_recovery/__snapshots__/jsfmt.spec.js.snap
+++ b/tests/typescript_error_recovery/__snapshots__/jsfmt.spec.js.snap
@@ -50,6 +50,260 @@ class f7<> {
 ================================================================================
 `;
 
+exports[`generic.ts 2`] = `
+====================================options=====================================
+parsers: ["typescript"]
+printWidth: 80
+trailingComma: "es5"
+                                                                                | printWidth
+=====================================input======================================
+f1<>();
+
+new f2<>();
+
+function f3<>() {}
+
+class f4 {
+    constructor<>() {}
+}
+
+const f5 = function<>() {}
+
+interface f6<> {
+    test<>();
+}
+
+class f7<> {
+    test<>() {}
+}
+
+=====================================output=====================================
+f1<>();
+
+new f2<>();
+
+function f3<>() {}
+
+class f4 {
+  constructor<>() {}
+}
+
+const f5 = function<>() {};
+
+interface f6<> {
+  test<>();
+}
+
+class f7<> {
+  test<>() {}
+}
+
+================================================================================
+`;
+
+exports[`generic.ts 3`] = `
+====================================options=====================================
+parsers: ["typescript"]
+printWidth: 80
+trailingComma: "all"
+                                                                                | printWidth
+=====================================input======================================
+f1<>();
+
+new f2<>();
+
+function f3<>() {}
+
+class f4 {
+    constructor<>() {}
+}
+
+const f5 = function<>() {}
+
+interface f6<> {
+    test<>();
+}
+
+class f7<> {
+    test<>() {}
+}
+
+=====================================output=====================================
+f1<>();
+
+new f2<>();
+
+function f3<>() {}
+
+class f4 {
+  constructor<>() {}
+}
+
+const f5 = function<>() {};
+
+interface f6<> {
+  test<>();
+}
+
+class f7<> {
+  test<>() {}
+}
+
+================================================================================
+`;
+
+exports[`index-signature.ts 1`] = `
+====================================options=====================================
+parsers: ["typescript"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+type A = { [key: string] };
+
+type TwoParams = {
+  [a: string, b: string]: string;
+};
+type ThreeParams = {
+  [a: string, b: string, c: string]: string;
+};
+
+type TooLong = {
+  [loooooooooooooooooooooooooong: string, looooooooooooooooooooooooooooooooooooooong: string]: string;
+}
+type TooLong81 = { [loooooooooooooooooooooooooong: string, loooooooooooooooooong: string]: string; }
+type TooLong80 = { [loooooooooooooooooooooooooong: string, looooooooooooooooong: string]: string; }
+
+=====================================output=====================================
+type A = { [key: string] };
+
+type TwoParams = {
+  [a: string, b: string]: string;
+};
+type ThreeParams = {
+  [a: string, b: string, c: string]: string;
+};
+
+type TooLong = {
+  [
+    loooooooooooooooooooooooooong: string,
+    looooooooooooooooooooooooooooooooooooooong: string
+  ]: string;
+};
+type TooLong81 = {
+  [
+    loooooooooooooooooooooooooong: string,
+    loooooooooooooooooong: string
+  ]: string;
+};
+type TooLong80 = {
+  [loooooooooooooooooooooooooong: string, looooooooooooooooong: string]: string;
+};
+
+================================================================================
+`;
+
+exports[`index-signature.ts 2`] = `
+====================================options=====================================
+parsers: ["typescript"]
+printWidth: 80
+trailingComma: "es5"
+                                                                                | printWidth
+=====================================input======================================
+type A = { [key: string] };
+
+type TwoParams = {
+  [a: string, b: string]: string;
+};
+type ThreeParams = {
+  [a: string, b: string, c: string]: string;
+};
+
+type TooLong = {
+  [loooooooooooooooooooooooooong: string, looooooooooooooooooooooooooooooooooooooong: string]: string;
+}
+type TooLong81 = { [loooooooooooooooooooooooooong: string, loooooooooooooooooong: string]: string; }
+type TooLong80 = { [loooooooooooooooooooooooooong: string, looooooooooooooooong: string]: string; }
+
+=====================================output=====================================
+type A = { [key: string] };
+
+type TwoParams = {
+  [a: string, b: string]: string;
+};
+type ThreeParams = {
+  [a: string, b: string, c: string]: string;
+};
+
+type TooLong = {
+  [
+    loooooooooooooooooooooooooong: string,
+    looooooooooooooooooooooooooooooooooooooong: string,
+  ]: string;
+};
+type TooLong81 = {
+  [
+    loooooooooooooooooooooooooong: string,
+    loooooooooooooooooong: string,
+  ]: string;
+};
+type TooLong80 = {
+  [loooooooooooooooooooooooooong: string, looooooooooooooooong: string]: string;
+};
+
+================================================================================
+`;
+
+exports[`index-signature.ts 3`] = `
+====================================options=====================================
+parsers: ["typescript"]
+printWidth: 80
+trailingComma: "all"
+                                                                                | printWidth
+=====================================input======================================
+type A = { [key: string] };
+
+type TwoParams = {
+  [a: string, b: string]: string;
+};
+type ThreeParams = {
+  [a: string, b: string, c: string]: string;
+};
+
+type TooLong = {
+  [loooooooooooooooooooooooooong: string, looooooooooooooooooooooooooooooooooooooong: string]: string;
+}
+type TooLong81 = { [loooooooooooooooooooooooooong: string, loooooooooooooooooong: string]: string; }
+type TooLong80 = { [loooooooooooooooooooooooooong: string, looooooooooooooooong: string]: string; }
+
+=====================================output=====================================
+type A = { [key: string] };
+
+type TwoParams = {
+  [a: string, b: string]: string;
+};
+type ThreeParams = {
+  [a: string, b: string, c: string]: string;
+};
+
+type TooLong = {
+  [
+    loooooooooooooooooooooooooong: string,
+    looooooooooooooooooooooooooooooooooooooong: string,
+  ]: string;
+};
+type TooLong81 = {
+  [
+    loooooooooooooooooooooooooong: string,
+    loooooooooooooooooong: string,
+  ]: string;
+};
+type TooLong80 = {
+  [loooooooooooooooooooooooooong: string, looooooooooooooooong: string]: string;
+};
+
+================================================================================
+`;
+
 exports[`jsdoc_only_types.ts 1`] = `
 ====================================options=====================================
 parsers: ["typescript"]
@@ -81,3 +335,69 @@ let j: (function(): string) | number;
 
 ================================================================================
 `;
+
+exports[`jsdoc_only_types.ts 2`] = `
+====================================options=====================================
+parsers: ["typescript"]
+printWidth: 80
+trailingComma: "es5"
+                                                                                | printWidth
+=====================================input======================================
+let a: *;
+function b(x: ?) {}
+let c: ?string;
+let d: string?;
+let e: ?(string | number);
+let f: !string;
+let g: string!;
+let h: !(string | number);
+let i: function(): string;
+let j: (function(): string) | number;
+
+=====================================output=====================================
+let a: *;
+function b(x: ?) {}
+let c: ?string;
+let d: ?string;
+let e: ?(string | number);
+let f: !string;
+let g: !string;
+let h: !(string | number);
+let i: function(): string;
+let j: (function(): string) | number;
+
+================================================================================
+`;
+
+exports[`jsdoc_only_types.ts 3`] = `
+====================================options=====================================
+parsers: ["typescript"]
+printWidth: 80
+trailingComma: "all"
+                                                                                | printWidth
+=====================================input======================================
+let a: *;
+function b(x: ?) {}
+let c: ?string;
+let d: string?;
+let e: ?(string | number);
+let f: !string;
+let g: string!;
+let h: !(string | number);
+let i: function(): string;
+let j: (function(): string) | number;
+
+=====================================output=====================================
+let a: *;
+function b(x: ?) {}
+let c: ?string;
+let d: ?string;
+let e: ?(string | number);
+let f: !string;
+let g: !string;
+let h: !(string | number);
+let i: function(): string;
+let j: (function(): string) | number;
+
+================================================================================
+`;
diff --git a/tests/typescript_error_recovery/index-signature.ts b/tests/typescript_error_recovery/index-signature.ts
new file mode 100644
index 000000000..896541357
--- /dev/null
+++ b/tests/typescript_error_recovery/index-signature.ts
@@ -0,0 +1,14 @@
+type A = { [key: string] };
+
+type TwoParams = {
+  [a: string, b: string]: string;
+};
+type ThreeParams = {
+  [a: string, b: string, c: string]: string;
+};
+
+type TooLong = {
+  [loooooooooooooooooooooooooong: string, looooooooooooooooooooooooooooooooooooooong: string]: string;
+}
+type TooLong81 = { [loooooooooooooooooooooooooong: string, loooooooooooooooooong: string]: string; }
+type TooLong80 = { [loooooooooooooooooooooooooong: string, looooooooooooooooong: string]: string; }
diff --git a/tests/typescript_error_recovery/jsfmt.spec.js b/tests/typescript_error_recovery/jsfmt.spec.js
index 2ea3bb6eb..9ae5dd616 100644
--- a/tests/typescript_error_recovery/jsfmt.spec.js
+++ b/tests/typescript_error_recovery/jsfmt.spec.js
@@ -1 +1,3 @@
 run_spec(__dirname, ["typescript"]);
+run_spec(__dirname, ["typescript"], { trailingComma: "es5" });
+run_spec(__dirname, ["typescript"], { trailingComma: "all" });