diff --git a/power-assert-formatter/power-assert-formatter-tests.ts b/power-assert-formatter/power-assert-formatter-tests.ts
new file mode 100644
index 000000000..cd5a2680d
--- /dev/null
+++ b/power-assert-formatter/power-assert-formatter-tests.ts
@@ -0,0 +1,5 @@
+/// <reference path="./power-assert-formatter.d.ts" />
+
+powerAssertFormatter();
+
+powerAssertFormatter({lineSeparator: '\n'});
diff --git a/power-assert-formatter/power-assert-formatter.d.ts b/power-assert-formatter/power-assert-formatter.d.ts
new file mode 100644
index 000000000..c5ad3b6f5
--- /dev/null
+++ b/power-assert-formatter/power-assert-formatter.d.ts
@@ -0,0 +1,29 @@
+// Type definitions for power-assert-formatter
+// Project: https://github.com/twada/power-assert-formatter
+// Definitions by: vvakame <https://github.com/vvakame>
+// Definitions: https://github.com/borisyankov/DefinitelyTyped
+
+declare function powerAssertFormatter(options?: powerAssertFormatter.Options): powerAssertFormatter.Formatter;
+
+declare module powerAssertFormatter {
+    export interface Options {
+        lineDiffThreshold?: number;
+        maxDepth?: number;
+        outputOffset?: number;
+        anonymous?: string;
+        circular?: string;
+        lineSeparator?: string;
+        ambiguousEastAsianCharWidth?: number;
+        widthOf?: Function;
+        stringify?: Function;
+        diff?: Function;
+        writerClass?: {new (): any;};
+        renderers?: any[]; // { string | Function }[]
+    }
+
+    export interface Formatter {
+        (powerAssertContext: any): string;
+    }
+
+    export function defaultOptions(): Options;
+}