diff --git a/types/atom/atom-tests.ts b/types/atom/atom-tests.ts
index 9bb03e4e60..8995bbd3fa 100644
--- a/types/atom/atom-tests.ts
+++ b/types/atom/atom-tests.ts
@@ -32,6 +32,7 @@ declare let editor: Atom.TextEditor;
 declare let editors: Atom.TextEditor[];
 declare let emitter: Atom.Emitter;
 declare let file: Atom.File;
+declare let fileOrDir: Atom.File | Atom.Directory;
 declare let grammar: Atom.Grammar;
 declare let grammars: Atom.Grammar[];
 declare let gutter: Atom.Gutter;
@@ -966,6 +967,16 @@ function testFile() {
     file.writeSync("Test");
 }
 
+// File/Directory Type Guarding ===============================================
+function testFileDirectoryTypeGuarding() {
+    if (fileOrDir.isFile()) {
+      file = fileOrDir;
+    }
+    if (fileOrDir.isDirectory()) {
+      dir = fileOrDir;
+    }
+}
+
 // GitRepository ==============================================================
 function testGitRepository() {
     // Construction and Destruction
diff --git a/types/atom/index.d.ts b/types/atom/index.d.ts
index b989671920..6cc3a30c77 100644
--- a/types/atom/index.d.ts
+++ b/types/atom/index.d.ts
@@ -3279,10 +3279,10 @@ export class Directory {
 
     // Directory Metadata
     /** Returns a boolean, always false. */
-    isFile(): boolean;
+    isFile(): this is File;
 
     /** Returns a roolean, always true. */
-    isDirectory(): boolean;
+    isDirectory(): this is Directory;
 
     /** Returns a boolean indicating whether or not this is a symbolic link. */
     isSymbolicLink(): boolean;
@@ -3496,10 +3496,10 @@ export class File {
 
     // File Metadata
     /** Returns a boolean, always true. */
-    isFile(): boolean;
+    isFile(): this is File;
 
     /** Returns a boolean, always false. */
-    isDirectory(): boolean;
+    isDirectory(): this is Directory;
 
     /** Returns a boolean indicating whether or not this is a symbolic link. */
     isSymbolicLink(): boolean;