diff --git a/lib/autocomplete.coffee b/lib/autocomplete.coffee
new file mode 100644
index 0000000..d33ffc3
--- /dev/null
+++ b/lib/autocomplete.coffee
@@ -0,0 +1,66 @@
+fs = require 'fs'
+path = require 'path'
+Ex = require './ex'
+
+module.exports =
+class AutoComplete
+  constructor: (commands) ->
+    @commands = commands
+    @resetCompletion()
+
+  resetCompletion: () ->
+    @autoCompleteIndex = 0
+    @autoCompleteText = null
+    @completions = []
+
+  getAutocomplete: (text) ->
+    if !@autoCompleteText
+      @autoCompleteText = text
+
+    parts = @autoCompleteText.split(' ')
+    cmd = parts[0]
+
+    if parts.length > 1
+      filePath = parts.slice(1).join(' ')
+      return @getCompletion(() => @getFilePathCompletion(cmd, filePath))
+    else
+      return @getCompletion(() => @getCommandCompletion(cmd))
+
+  filterByPrefix: (commands, prefix) ->
+    commands.filter((f) => f.startsWith(prefix))
+
+  getCompletion: (completeFunc) ->
+    if @completions.length == 0
+      @completions = completeFunc()
+
+    if @completions.length
+      complete = @completions[@autoCompleteIndex % @completions.length]
+      @autoCompleteIndex++
+
+      # Only one result so lets return this directory
+      if complete.endsWith('/') && @completions.length == 1
+        @resetCompletion()
+
+      return complete
+
+  getCommandCompletion: (command) ->
+    if @completions.length == 0
+      return @filterByPrefix(@commands, command)
+
+  getFilePathCompletion: (command, filePath) ->
+      if filePath.endsWith(path.sep)
+        basePath = path.dirname(filePath + '.')
+        baseName = ''
+      else
+        basePath = path.dirname(filePath)
+        baseName = path.basename(filePath)
+
+      files = fs.readdirSync(basePath)
+
+      return @filterByPrefix(files, baseName).map((f) =>
+        filePath = path.join(basePath, f)
+        if fs.lstatSync(filePath).isDirectory()
+          return command + ' ' + filePath  + path.sep
+        else
+          return command + ' ' + filePath
+      )
diff --git a/lib/ex-view-model.coffee b/lib/ex-view-model.coffee
index 0c99be9..c8f1202 100644
--- a/lib/ex-view-model.coffee
+++ b/lib/ex-view-model.coffee
@@ -1,4 +1,6 @@
 {ViewModel, Input} = require './view-model'
+AutoComplete = require './autocomplete'
+Ex = require './ex'
 
 module.exports =
 class ExViewModel extends ViewModel
@@ -6,15 +8,31 @@ class ExViewModel extends ViewModel
     super(@exCommand, class: 'command')
     @historyIndex = -1
 
+    @view.editorElement.addEventListener('keydown', @tabAutocomplete)
     atom.commands.add(@view.editorElement, 'core:move-up', @increaseHistoryEx)
     atom.commands.add(@view.editorElement, 'core:move-down', @decreaseHistoryEx)
 
+    @autoComplete = new AutoComplete(Ex.getCommands())
+
   restoreHistory: (index) ->
     @view.editorElement.getModel().setText(@history(index).value)
 
   history: (index) ->
     @exState.getExHistoryItem(index)
 
+  tabAutocomplete: (event) =>
+    if event.keyCode == 9
+      event.stopPropagation()
+      event.preventDefault()
+
+      completed = @autoComplete.getAutocomplete(@view.editorElement.getModel().getText())
+      if completed
+        @view.editorElement.getModel().setText(completed)
+
+      return false
+    else
+      @autoComplete.resetCompletion()
+
   increaseHistoryEx: =>
     if @history(@historyIndex + 1)?
       @historyIndex += 1
diff --git a/lib/ex.coffee b/lib/ex.coffee
index c91beb7..0e46110 100644
--- a/lib/ex.coffee
+++ b/lib/ex.coffee
@@ -109,6 +109,9 @@ class Ex
   @registerAlias: (alias, name) =>
     @singleton()[alias] = (args) => @singleton()[name](args)
 
+  @getCommands: () =>
+    Object.keys(@singleton())
+
   quit: ->
     atom.workspace.getActivePane().destroyActiveItem()
 
diff --git a/spec/autocomplete-spec.coffee b/spec/autocomplete-spec.coffee
new file mode 100644
index 0000000..49b5a1e
--- /dev/null
+++ b/spec/autocomplete-spec.coffee
@@ -0,0 +1,82 @@
+fs = require 'fs-plus'
+path = require 'path'
+os = require 'os'
+uuid = require 'node-uuid'
+
+helpers = require './spec-helper'
+AutoComplete = require '../lib/autocomplete'
+
+describe "autocomplete functionality", ->
+  beforeEach ->
+    @autoComplete = new AutoComplete(['taba', 'tabb', 'tabc'])
+    @testDir = path.join(os.tmpdir(), "atom-ex-mode-spec-#{uuid.v4()}")
+    @testFile1 = path.join(@testDir, "atom-ex-testfile-a.txt")
+    @testFile2 = path.join(@testDir, "atom-ex-testfile-b.txt")
+
+    runs =>
+      fs.makeTreeSync(@testDir)
+      fs.closeSync(fs.openSync(@testFile1, 'w'));
+      fs.closeSync(fs.openSync(@testFile2, 'w'));
+      spyOn(@autoComplete, 'resetCompletion').andCallThrough()
+      spyOn(@autoComplete, 'getFilePathCompletion').andCallThrough()
+      spyOn(@autoComplete, 'getCommandCompletion').andCallThrough()
+
+  afterEach ->
+    fs.removeSync(@testDir)
+
+  describe "autocomplete commands", ->
+    beforeEach ->
+      @completed = @autoComplete.getAutocomplete('tab')
+
+    it "returns taba", ->
+      expect(@completed).toEqual('taba')
+
+    it "calls command function", ->
+      expect(@autoComplete.getCommandCompletion.callCount).toBe(1)
+
+  describe "autocomplete commands, then autoComplete again", ->
+    beforeEach ->
+      @completed = @autoComplete.getAutocomplete('tab')
+      @completed = @autoComplete.getAutocomplete('tab')
+
+    it "returns tabb", ->
+      expect(@completed).toEqual('tabb')
+
+    it "calls command function", ->
+      expect(@autoComplete.getCommandCompletion.callCount).toBe(1)
+
+  describe "autocomplete directory", ->
+    beforeEach ->
+      filePath = path.join(os.tmpdir(), 'atom-ex-mode-spec-')
+      @completed = @autoComplete.getAutocomplete('tabe ' + filePath)
+
+    it "returns testDir", ->
+      expected = 'tabe ' + @testDir + path.sep
+      expect(@completed).toEqual(expected)
+
+    it "clears autocomplete", ->
+      expect(@autoComplete.resetCompletion.callCount).toBe(1)
+
+  describe "autocomplete directory, then autocomplete again", ->
+    beforeEach ->
+      filePath = path.join(os.tmpdir(), 'atom-ex-mode-spec-')
+      @completed = @autoComplete.getAutocomplete('tabe ' + filePath)
+      @completed = @autoComplete.getAutocomplete(@completed)
+
+    it "returns test file 1", ->
+      expect(@completed).toEqual('tabe ' + @testFile1)
+
+    it "lists files twice", ->
+      expect(@autoComplete.getFilePathCompletion.callCount).toBe(2)
+
+  describe "autocomplete full directory, then autocomplete again", ->
+    beforeEach ->
+      filePath = path.join(@testDir, 'a')
+      @completed = @autoComplete.getAutocomplete('tabe ' + filePath)
+      @completed = @autoComplete.getAutocomplete(@completed)
+
+    it "returns test file 2", ->
+      expect(@completed).toEqual('tabe ' + @testFile2)
+
+    it "lists files once", ->
+      expect(@autoComplete.getFilePathCompletion.callCount).toBe(1)