--- a/testing/mozbase/mozinfo/mozinfo/mozinfo.py
+++ b/testing/mozbase/mozinfo/mozinfo/mozinfo.py
@@ -196,23 +196,30 @@ def update(new_info):
     if isLinux or isBsd:
         globals()['isUnix'] = True
 
 def find_and_update_from_json(*dirs):
     """
     Find a mozinfo.json file, load it, and update the info with the
     contents.
 
-    :param dirs: Directories in which to look for the file. They will be
-                 searched after first looking in the root of the objdir
-                 if the current script is being run from a Mozilla objdir.
+    The search strategy is as follows. The first available file is used.
+
+    1) MOZINFO_PATH environment variable.
+    2) objdir (via a build system context)
+    3) Traversing directories ``dirs`` for a mozinfo.json file.
 
     Returns the full path to mozinfo.json if it was found, or None otherwise.
     """
-    # First, see if we're in an objdir
+    env_path = _os.environ.get('MOZINFO_PATH', None)
+    if env_path:
+        # Will raise if path does not exist or can't be loaded.
+        update(env_path)
+        return env_path
+
     try:
         from mozbuild.base import MozbuildObject, BuildEnvironmentNotFoundException
         build = MozbuildObject.from_environment()
         json_path = _os.path.join(build.topobjdir, "mozinfo.json")
         if _os.path.isfile(json_path):
             update(json_path)
             return json_path
     except ImportError:

--- a/testing/mozbase/mozinfo/tests/test.py
+++ b/testing/mozbase/mozinfo/tests/test.py
@@ -48,16 +48,31 @@ class TestMozinfo(unittest.TestCase):
 
     def test_update_file_invalid_json(self):
         """Test that mozinfo.update handles invalid JSON correctly"""
         j = os.path.join(self.tempdir,'test.json')
         with open(j, 'w') as f:
             f.write('invalid{"json":')
         self.assertRaises(ValueError,mozinfo.update,[j])
 
+    def test_find_and_update_file_env(self):
+        """mozinfo.find_and_update_json finds path from environment variable."""
+        j = os.path.join(self.tempdir, 'explicit_mozinfo.json')
+        with open(j, 'w') as fh:
+            json.dump({'foo': 'environment'}, fh)
+
+        old_env = dict(os.environ)
+        try:
+            os.environ['MOZINFO_PATH'] = j
+            self.assertEqual(mozinfo.find_and_update_from_json(), j)
+            self.assertEqual(mozinfo.info['foo'], 'environment')
+        finally:
+            os.environ.clear()
+            os.environ.update(old_env)
+
     def test_find_and_update_file(self):
         """Test that mozinfo.find_and_update_from_json can
         find mozinfo.json in a directory passed to it."""
         j = os.path.join(self.tempdir, "mozinfo.json")
         with open(j, "w") as f:
             f.write(json.dumps({"foo": "abcdefg"}))
         self.assertEqual(mozinfo.find_and_update_from_json(self.tempdir), j)
         self.assertEqual(mozinfo.info["foo"], "abcdefg")