diff --git a/PIL/IcoImagePlugin.py b/PIL/IcoImagePlugin.py
index 2dc46ea18..145816094 100644
--- a/PIL/IcoImagePlugin.py
+++ b/PIL/IcoImagePlugin.py
@@ -24,6 +24,9 @@
 
 __version__ = "0.1"
 
+import struct
+from io import BytesIO
+
 from PIL import Image, ImageFile, BmpImagePlugin, PngImagePlugin, _binary
 from math import log, ceil
 
@@ -37,6 +40,42 @@ i32 = _binary.i32le
 _MAGIC = b"\0\0\1\0"
 
 
+def _save(im, fp, filename):
+    fp.write(_MAGIC)  # (2+2)
+    sizes = im.encoderinfo.get("sizes",
+                               [(16, 16), (24, 24), (32, 32), (48, 48),
+                                (64, 64), (128, 128), (255, 255)])
+    width, height = im.size
+    filter(lambda x: False if (x[0] > width or x[1] > height or
+                               x[0] > 255 or x[1] > 255) else True, sizes)
+    sizes = sorted(sizes, key=lambda x: x[0])
+    fp.write(struct.pack("H", len(sizes)))  # idCount(2)
+    offset = fp.tell() + len(sizes)*16
+    for size in sizes:
+        width, height = size
+        fp.write(struct.pack("B", width))  # bWidth(1)
+        fp.write(struct.pack("B", height))  # bHeight(1)
+        fp.write(b"\0")  # bColorCount(1)
+        fp.write(b"\0")  # bReserved(1)
+        fp.write(b"\0\0")  # wPlanes(2)
+        fp.write(struct.pack("H", 32))  # wBitCount(2)
+
+        image_io = BytesIO()
+        tmp = im.copy()
+        tmp.thumbnail(size, Image.ANTIALIAS)
+        tmp.save(image_io, "png")
+        image_io.seek(0)
+        image_bytes = image_io.read()
+        bytes_len = len(image_bytes)
+        fp.write(struct.pack("I", bytes_len))  # dwBytesInRes(4)
+        fp.write(struct.pack("I", offset))  # dwImageOffset(4)
+        current = fp.tell()
+        fp.seek(offset)
+        fp.write(image_bytes)
+        offset = offset + bytes_len
+        fp.seek(current)
+
+
 def _accept(prefix):
     return prefix[:4] == _MAGIC
 
@@ -241,4 +280,5 @@ class IcoImageFile(ImageFile.ImageFile):
 # --------------------------------------------------------------------
 
 Image.register_open("ICO", IcoImageFile, _accept)
+Image.register_save("ICO", _save)
 Image.register_extension("ICO", ".ico")
diff --git a/Tests/test_file_ico.py b/Tests/test_file_ico.py
index 12f4ed3f3..01d3f5904 100644
--- a/Tests/test_file_ico.py
+++ b/Tests/test_file_ico.py
@@ -1,5 +1,6 @@
-from helper import unittest, PillowTestCase
+from helper import unittest, PillowTestCase, hopper
 
+import io
 from PIL import Image
 
 # sample ppm stream
@@ -16,6 +17,32 @@ class TestFileIco(PillowTestCase):
         self.assertEqual(im.size, (16, 16))
         self.assertEqual(im.format, "ICO")
 
+    def test_save_to_bytes(self):
+        output = io.BytesIO()
+        im = hopper()
+        im.save(output, "ico", sizes=[(32, 32), (64, 64)])
+
+        # the default image
+        output.seek(0)
+        reloaded = Image.open(output)
+        self.assertEqual(reloaded.info['sizes'],set([(32, 32), (64, 64)]))
+
+        self.assertEqual(im.mode, reloaded.mode)
+        self.assertEqual((64, 64), reloaded.size)
+        self.assertEqual(reloaded.format, "ICO")
+        self.assert_image_equal(reloaded, hopper().resize((64,64), Image.ANTIALIAS))
+
+        # the other one
+        output.seek(0)
+        reloaded = Image.open(output)
+        reloaded.size = (32,32)
+
+        self.assertEqual(im.mode, reloaded.mode)
+        self.assertEqual((32, 32), reloaded.size)
+        self.assertEqual(reloaded.format, "ICO")
+        self.assert_image_equal(reloaded, hopper().resize((32,32), Image.ANTIALIAS))
+        
+        
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/docs/handbook/image-file-formats.rst b/docs/handbook/image-file-formats.rst
index 50eecd9da..a1961fa7c 100644
--- a/docs/handbook/image-file-formats.rst
+++ b/docs/handbook/image-file-formats.rst
@@ -589,6 +589,14 @@ ICO
 
 ICO is used to store icons on Windows. The largest available icon is read.
 
+The :py:meth:`~PIL.Image.Image.save` method supports the following options:
+
+**sizes**
+    A list of sizes including in this ico file; these are a 2-tuple,
+    ``(width, height)``; Default to ``[(16, 16), (24, 24), (32, 32), (48, 48),
+    (64, 64), (128, 128), (255, 255)]``. Any size is bigger then the original
+    size or 255 will be ignored.
+
 ICNS
 ^^^^