diff --git a/onionshare/onionshare.py b/onionshare/onionshare.py
index afc6a3fc..be08910b 100644
--- a/onionshare/onionshare.py
+++ b/onionshare/onionshare.py
@@ -238,6 +238,12 @@ def main():
     web.set_file_info(filenames)
     app.cleanup_filenames.append(web.zip_filename)
 
+    # warn about sending large files over Tor
+    if web.zip_filesize >= 209715200: # 200mb
+        print ''
+        print strings._("large_filesize").format(helpers.human_readable_filesize(web.zip_filesize))
+        print ''
+
     # start onionshare service in new thread
     t = threading.Thread(target=web.start, args=(app.port, app.stay_open))
     t.daemon = True
diff --git a/onionshare/strings.json b/onionshare/strings.json
index cc1bf290..f675df57 100644
--- a/onionshare/strings.json
+++ b/onionshare/strings.json
@@ -21,6 +21,7 @@
     "close_on_finish": "Stop server automatically",
     "choose_file": "Choose a file to share",
     "closing_automatically": "Closing automatically because download finished",
+    "large_filesize": "You are sending a total of {0}. Transferring large files using OnionShare might take hours.",
     "error_tails_invalid_port": "Invalid value, port must be an integer",
     "error_tails_unknown_root": "Unknown error with Tails root process",
     "help_tails_port": "Tails only: port for opening firewall, starting hidden service",