--- a/testing/mozharness/configs/unittests/mac_unittest.py
+++ b/testing/mozharness/configs/unittests/mac_unittest.py
@@ -81,16 +81,17 @@ config = {
                 "--extra-profile-file=tests/bin/plugins",
                 "--symbols-path=%(symbols_path)s",
                 "--certificate-path=tests/certs",
                 "--quiet",
                 "--log-raw=%(raw_log_file)s",
                 "--log-errorsummary=%(error_summary_file)s",
                 "--screenshot-on-fail",
                 "--cleanup-crashes",
+                "--marionette-startup-timeout=180",
                 "--work-path=%(abs_work_dir)s",
             ],
             "run_filename": "runtests.py",
             "testsdir": "mochitest"
         },
         "mozbase": {
             "options": [
                 "-b",

--- a/testing/mozharness/configs/unittests/win_taskcluster_unittest.py
+++ b/testing/mozharness/configs/unittests/win_taskcluster_unittest.py
@@ -94,16 +94,17 @@ config = {
                 "--extra-profile-file=tests/bin/plugins",
                 "--symbols-path=%(symbols_path)s",
                 "--certificate-path=tests/certs",
                 "--quiet",
                 "--log-raw=%(raw_log_file)s",
                 "--log-errorsummary=%(error_summary_file)s",
                 "--screenshot-on-fail",
                 "--cleanup-crashes",
+                "--marionette-startup-timeout=180",
             ],
             "run_filename": "runtests.py",
             "testsdir": "mochitest"
         },
         "mozbase": {
             "options": [
                 "-b",
                 "%(binary_path)s"