diff --git a/mercurial/cmdutil.py b/mercurial/cmdutil.py
--- a/mercurial/cmdutil.py
+++ b/mercurial/cmdutil.py
@@ -1812,11 +1812,12 @@ def forget(ui, repo, match, prefix, expl
     forgot.extend(forget)
     return bad, forgot
 
-def cat(ui, repo, ctx, matcher, **opts):
+def cat(ui, repo, ctx, matcher, prefix, **opts):
     err = 1
 
     def write(path):
-        fp = makefileobj(repo, opts.get('output'), ctx.node(), pathname=path)
+        fp = makefileobj(repo, opts.get('output'), ctx.node(),
+                         pathname=os.path.join(prefix, path))
         data = ctx[path].data()
         if opts.get('decode'):
             data = repo.wwritedata(path, data)
@@ -1833,9 +1834,35 @@ def cat(ui, repo, ctx, matcher, **opts):
             write(file)
             return 0
 
+    # Don't warn about "missing" files that are really in subrepos
+    bad = matcher.bad
+
+    def badfn(path, msg):
+        for subpath in ctx.substate:
+            if path.startswith(subpath):
+                return
+        bad(path, msg)
+
+    matcher.bad = badfn
+
     for abs in ctx.walk(matcher):
         write(abs)
         err = 0
+
+    matcher.bad = bad
+
+    for subpath in sorted(ctx.substate):
+        sub = ctx.sub(subpath)
+        try:
+            submatch = matchmod.narrowmatcher(subpath, matcher)
+
+            if not sub.cat(ui, submatch, os.path.join(prefix, sub._path),
+                           **opts):
+                err = 0
+        except error.RepoLookupError:
+            ui.status(_("skipping missing subrepository: %s\n")
+                           % os.path.join(prefix, subpath))
+
     return err
 
 def duplicatecopies(repo, rev, fromrev):
diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -1174,7 +1174,7 @@ def cat(ui, repo, file1, *pats, **opts):
     ctx = scmutil.revsingle(repo, opts.get('rev'))
     m = scmutil.match(ctx, (file1,) + pats, opts)
 
-    return cmdutil.cat(ui, repo, ctx, m, **opts)
+    return cmdutil.cat(ui, repo, ctx, m, '', **opts)
 
 @command('^clone',
     [('U', 'noupdate', None,
diff --git a/mercurial/help/subrepos.txt b/mercurial/help/subrepos.txt
--- a/mercurial/help/subrepos.txt
+++ b/mercurial/help/subrepos.txt
@@ -84,6 +84,9 @@ Interaction with Mercurial Commands
 :archive: archive does not recurse in subrepositories unless
     -S/--subrepos is specified.
 
+:cat: cat currently only handles exact file matches in subrepos.
+    Git and Subversion subrepositories are currently ignored.
+
 :commit: commit creates a consistent snapshot of the state of the
     entire project and its subrepositories. If any subrepositories
     have been modified, Mercurial will abort.  Mercurial can be made
diff --git a/mercurial/subrepo.py b/mercurial/subrepo.py
--- a/mercurial/subrepo.py
+++ b/mercurial/subrepo.py
@@ -439,6 +439,9 @@ class abstractsubrepo(object):
     def add(self, ui, match, dryrun, listsubrepos, prefix, explicitonly):
         return []
 
+    def cat(self, ui, match, prefix, **opts):
+        return 1
+
     def status(self, rev2, **opts):
         return [], [], [], [], [], [], []
 
@@ -609,6 +612,12 @@ class hgsubrepo(abstractsubrepo):
                            os.path.join(prefix, self._path), explicitonly)
 
     @annotatesubrepoerror
+    def cat(self, ui, match, prefix, **opts):
+        rev = self._state[1]
+        ctx = self._repo[rev]
+        return cmdutil.cat(ui, self._repo, ctx, match, prefix, **opts)
+
+    @annotatesubrepoerror
     def status(self, rev2, **opts):
         try:
             rev1 = self._state[1]
diff --git a/tests/test-subrepo.t b/tests/test-subrepo.t
--- a/tests/test-subrepo.t
+++ b/tests/test-subrepo.t
@@ -792,6 +792,19 @@ Prepare a repo with subrepo
   $ echo test >> sub/repo/foo
   $ hg ci -mtest
   committing subrepository sub/repo (glob)
+  $ hg cat sub/repo/foo
+  test
+  test
+  $ mkdir -p tmp/sub/repo
+  $ hg cat -r 0 --output tmp/%p_p sub/repo/foo
+  $ cat tmp/sub/repo/foo_p
+  test
+  $ mv sub/repo sub_
+  $ hg cat sub/repo/baz
+  skipping missing subrepository: sub/repo
+  [1]
+  $ rm -rf sub/repo
+  $ mv sub_ sub/repo
   $ cd ..
 
 Create repo without default path, pull top repo, and see what happens on update