diff --git a/git_rebase_update.py b/git_rebase_update.py
index f2b47b894c..46d16064e6 100755
--- a/git_rebase_update.py
+++ b/git_rebase_update.py
@@ -232,6 +232,16 @@ def rebase_branch(branch, parent, start_hash):
     return True
 
 
+def with_downstream_branches(base_branches, branch_tree):
+    """Returns a set of base_branches and all downstream branches."""
+    downstream_branches = set()
+    for branch, parent in git.topo_iter(branch_tree):
+        if parent in base_branches or parent in downstream_branches:
+            downstream_branches.add(branch)
+
+    return downstream_branches.union(base_branches)
+
+
 def main(args=None):
     if gclient_utils.IsEnvCog():
         print(
@@ -253,6 +263,10 @@ def main(args=None):
     parser.add_argument('--current',
                         action='store_true',
                         help='Only rebase the current branch.')
+    parser.add_argument('--tree',
+                        action='store_true',
+                        help='Rebase all branches downstream from the '
+                        'selected branch(es).')
     parser.add_argument('branches',
                         nargs='*',
                         help='Branches to be rebased. All branches are assumed '
@@ -297,6 +311,10 @@ def main(args=None):
         branches_to_rebase.add(git.current_branch())
 
     skipped, branch_tree = git.get_branch_tree(use_limit=not opts.current)
+    if opts.tree:
+        branches_to_rebase = with_downstream_branches(branches_to_rebase,
+                                                      branch_tree)
+
     if branches_to_rebase:
         skipped = set(skipped).intersection(branches_to_rebase)
     for branch in skipped:
diff --git a/man/src/git-rebase-update.txt b/man/src/git-rebase-update.txt
index e7c0c2d2fd..3f07fdc5ea 100644
--- a/man/src/git-rebase-update.txt
+++ b/man/src/git-rebase-update.txt
@@ -85,6 +85,10 @@ OPTIONS
 --current::
   Only rebase the current branch.
 
+--tree::
+  Also rebase any branches downstream from the selected branches. Use with
+  named branches or `--current` to selectively rebase a branch tree.
+
 
 CONFIGURATION VARIABLES
 -----------------------