diff --git a/tests/test-treemanifest-prefetch.t b/tests/test-treemanifest-prefetch.t
--- a/tests/test-treemanifest-prefetch.t
+++ b/tests/test-treemanifest-prefetch.t
@@ -368,3 +368,39 @@
   $ rm -rf $CACHEDIR/master
   $ hg prefetchtrees -r '2 + 4'
   5 trees fetched over * (glob)
+
+Test repack option
+  $ rm -rf $CACHEDIR/master
+
+  $ hg prefetchtrees -r '0'
+  2 trees fetched over *s (glob)
+  $ hg prefetchtrees -r '2'
+  3 trees fetched over *s (glob)
+
+  $ hg prefetchtrees -r '4' --repack
+  3 trees fetched over *s (glob)
+  (running background incremental repack)
+
+  $ sleep 0.5
+  $ hg debugwaitonrepack
+  $ hg debugdatapack $CACHEDIR/master/packs/manifests/*.dataidx
+  $TESTTMP/hgcache/master/packs/manifests/70490b37ec1bf0862806062b34af9ad608268dc2:
+  (empty name):
+  Node          Delta Base    Delta Length  Blob Size
+  ef362f8bbe8a  000000000000  46            46
+  aa52a49be522  000000000000  95            95
+  60a7f7acb6bb  000000000000  95            95
+  
+  Total:                      236           236       (0.0% bigger)
+  dir:
+  Node          Delta Base    Delta Length  Blob Size
+  bf22bc15398b  000000000000  43            43
+  a18d21674e76  000000000000  43            43
+  bc0c2c938b92  a18d21674e76  55            43
+  
+  Total:                      141           129       (9.3% bigger)
+  subdir:
+  Node          Delta Base    Delta Length  Blob Size
+  ddb35f099a64  000000000000  43            43
+  
+  Total:                      43            43        (0.0% bigger)
diff --git a/treemanifest/__init__.py b/treemanifest/__init__.py
--- a/treemanifest/__init__.py
+++ b/treemanifest/__init__.py
@@ -113,6 +113,7 @@
     _computeincrementalhistorypack,
     _runrepack,
     _topacks,
+    backgroundrepack,
 )
 import cstore
 
@@ -988,6 +989,7 @@
 
 @command('prefetchtrees', [
     ('r', 'rev', '', _("revs to prefetch the trees for")),
+    ('', 'repack', False, _('run repack after prefetch')),
     ('b', 'base', '', _("rev that is assumed to already be local")),
     ] + commands.walkopts, _('--rev REVS PATTERN..'))
 def prefetchtrees(ui, repo, *args, **opts):
@@ -1003,6 +1005,10 @@
 
     _prefetchtrees(repo, '', mfnodes, basemfnode, [])
 
+    # Run repack in background
+    if opts.get('repack'):
+        backgroundrepack(repo, incremental=True)
+
 def _prefetchtrees(repo, rootdir, mfnodes, basemfnodes, directories):
     # If possible, use remotefilelog's more expressive fallbackpath
     if util.safehasattr(repo, 'fallbackpath'):