diff --git a/manifest_xml.py b/manifest_xml.py
index 0859e1f..73e3496 100644
--- a/manifest_xml.py
+++ b/manifest_xml.py
@@ -393,6 +393,10 @@
   def IsArchive(self):
     return self.manifestProject.config.GetBoolean('repo.archive')
 
+  @property
+  def HasSubmodules(self):
+    return self.manifestProject.config.GetBoolean('repo.submodules')
+
   def _Unload(self):
     self._loaded = False
     self._projects = {}
diff --git a/project.py b/project.py
index 0d60fc6..e3185b8 100644
--- a/project.py
+++ b/project.py
@@ -1198,7 +1198,8 @@
                        no_tags=False,
                        archive=False,
                        optimized_fetch=False,
-                       prune=False):
+                       prune=False,
+                       submodules=False):
     """Perform only the network IO portion of the sync process.
        Local working directory/branch state is not affected.
     """
@@ -1275,7 +1276,8 @@
     if (need_to_fetch and
         not self._RemoteFetch(initial=is_new, quiet=quiet, alt_dir=alt_dir,
                               current_branch_only=current_branch_only,
-                              no_tags=no_tags, prune=prune, depth=depth)):
+                              no_tags=no_tags, prune=prune, depth=depth,
+                              submodules=submodules)):
       return False
 
     if self.worktree:
@@ -1331,11 +1333,11 @@
       raise ManifestInvalidRevisionError('revision %s in %s not found' %
                                          (self.revisionExpr, self.name))
 
-  def Sync_LocalHalf(self, syncbuf, force_sync=False):
+  def Sync_LocalHalf(self, syncbuf, force_sync=False, submodules=False):
     """Perform only the local IO portion of the sync process.
        Network access is not required.
     """
-    self._InitWorkTree(force_sync=force_sync)
+    self._InitWorkTree(force_sync=force_sync, submodules=submodules)
     all_refs = self.bare_ref.all
     self.CleanPublishedCache(all_refs)
     revid = self.GetRevisionId(all_refs)
@@ -1344,6 +1346,9 @@
       self._FastForward(revid)
       self._CopyAndLinkFiles()
 
+    def _dosubmodules():
+      self._SyncSubmodules(quiet=True)
+
     head = self.work_git.GetHead()
     if head.startswith(R_HEADS):
       branch = head[len(R_HEADS):]
@@ -1377,6 +1382,8 @@
 
       try:
         self._Checkout(revid, quiet=True)
+        if submodules:
+          self._SyncSubmodules(quiet=True)
       except GitError as e:
         syncbuf.fail(self, e)
         return
@@ -1401,6 +1408,8 @@
                    branch.name)
       try:
         self._Checkout(revid, quiet=True)
+        if submodules:
+          self._SyncSubmodules(quiet=True)
       except GitError as e:
         syncbuf.fail(self, e)
         return
@@ -1426,6 +1435,8 @@
         # strict subset.  We can fast-forward safely.
         #
         syncbuf.later1(self, _doff)
+        if submodules:
+          syncbuf.later1(self, _dosubmodules)
         return
 
     # Examine the local commits not in the remote.  Find the
@@ -1477,19 +1488,28 @@
     branch.Save()
 
     if cnt_mine > 0 and self.rebase:
+      def _docopyandlink():
+        self._CopyAndLinkFiles()
+
       def _dorebase():
         self._Rebase(upstream='%s^1' % last_mine, onto=revid)
-        self._CopyAndLinkFiles()
       syncbuf.later2(self, _dorebase)
+      if submodules:
+        syncbuf.later2(self, _dosubmodules)
+      syncbuf.later2(self, _docopyandlink)
     elif local_changes:
       try:
         self._ResetHard(revid)
+        if submodules:
+          self._SyncSubmodules(quiet=True)
         self._CopyAndLinkFiles()
       except GitError as e:
         syncbuf.fail(self, e)
         return
     else:
       syncbuf.later1(self, _doff)
+      if submodules:
+        syncbuf.later1(self, _dosubmodules)
 
   def AddCopyFile(self, src, dest, absdest):
     # dest should already be an absolute path, but src is project relative
@@ -1892,7 +1912,8 @@
                    alt_dir=None,
                    no_tags=False,
                    prune=False,
-                   depth=None):
+                   depth=None,
+                   submodules=False):
 
     is_sha1 = False
     tag_name = None
@@ -2004,6 +2025,9 @@
     if prune:
       cmd.append('--prune')
 
+    if submodules:
+      cmd.append('--recurse-submodules=on-demand')
+
     spec = []
     if not current_branch_only:
       # Fetch whole repo
@@ -2224,6 +2248,13 @@
     if GitCommand(self, cmd).Wait() != 0:
       raise GitError('%s reset --hard %s ' % (self.name, rev))
 
+  def _SyncSubmodules(self, quiet=True):
+    cmd = ['submodule', 'update', '--init', '--recursive']
+    if quiet:
+      cmd.append('-q')
+    if GitCommand(self, cmd).Wait() != 0:
+      raise GitError('%s submodule update --init --recursive %s ' % self.name)
+
   def _Rebase(self, upstream, onto=None):
     cmd = ['rebase']
     if onto is not None:
@@ -2464,7 +2495,7 @@
         else:
           raise
 
-  def _InitWorkTree(self, force_sync=False):
+  def _InitWorkTree(self, force_sync=False, submodules=False):
     dotgit = os.path.join(self.worktree, '.git')
     init_dotgit = not os.path.exists(dotgit)
     try:
@@ -2479,7 +2510,7 @@
         if force_sync:
           try:
             shutil.rmtree(dotgit)
-            return self._InitWorkTree(force_sync=False)
+            return self._InitWorkTree(force_sync=False, submodules=submodules)
           except:
             raise e
         raise e
@@ -2493,6 +2524,8 @@
         if GitCommand(self, cmd).Wait() != 0:
           raise GitError("cannot initialize work tree")
 
+        if submodules:
+          self._SyncSubmodules(quiet=True)
         self._CopyAndLinkFiles()
     except Exception:
       if init_dotgit:
diff --git a/repo b/repo
index dcd48e0..c1d8619 100755
--- a/repo
+++ b/repo
@@ -192,6 +192,9 @@
                  dest='archive', action='store_true',
                  help='checkout an archive instead of a git repository for '
                       'each project. See git archive.')
+group.add_option('--submodules',
+                 dest='submodules', action='store_true',
+                 help='sync any submodules associated with the manifest repo')
 group.add_option('-g', '--groups',
                  dest='groups', default='default',
                  help='restrict manifest projects to ones with specified '
diff --git a/subcmds/init.py b/subcmds/init.py
index bb7187d..b260ec0 100644
--- a/subcmds/init.py
+++ b/subcmds/init.py
@@ -111,6 +111,9 @@
                  dest='archive', action='store_true',
                  help='checkout an archive instead of a git repository for '
                       'each project. See git archive.')
+    g.add_option('--submodules',
+                 dest='submodules', action='store_true',
+                 help='sync any submodules associated with the manifest repo')
     g.add_option('-g', '--groups',
                  dest='groups', default='default',
                  help='restrict manifest projects to ones with specified '
@@ -236,10 +239,13 @@
               'in another location.', file=sys.stderr)
         sys.exit(1)
 
+    if opt.submodules:
+      m.config.SetString('repo.submodules', 'true')
+
     if not m.Sync_NetworkHalf(is_new=is_new, quiet=opt.quiet,
         clone_bundle=not opt.no_clone_bundle,
         current_branch_only=opt.current_branch_only,
-        no_tags=opt.no_tags):
+        no_tags=opt.no_tags, submodules=opt.submodules):
       r = m.GetRemote(m.remote.name)
       print('fatal: cannot obtain manifest %s' % r.url, file=sys.stderr)
 
@@ -253,7 +259,7 @@
       m.MetaBranchSwitch()
 
     syncbuf = SyncBuffer(m.config)
-    m.Sync_LocalHalf(syncbuf)
+    m.Sync_LocalHalf(syncbuf, submodules=opt.submodules)
     syncbuf.Finish()
 
     if is_new or m.CurrentBranch is None:
diff --git a/subcmds/sync.py b/subcmds/sync.py
index 8e8529e..82056f3 100644
--- a/subcmds/sync.py
+++ b/subcmds/sync.py
@@ -723,11 +723,12 @@
       mp.Sync_NetworkHalf(quiet=opt.quiet,
                           current_branch_only=opt.current_branch_only,
                           no_tags=opt.no_tags,
-                          optimized_fetch=opt.optimized_fetch)
+                          optimized_fetch=opt.optimized_fetch,
+                          submodules=self.manifest.HasSubmodules)
 
     if mp.HasChanges:
       syncbuf = SyncBuffer(mp.config)
-      mp.Sync_LocalHalf(syncbuf)
+      mp.Sync_LocalHalf(syncbuf, submodules=self.manifest.HasSubmodules)
       if not syncbuf.Finish():
         sys.exit(1)
       self._ReloadManifest(manifest_name)