diff --git a/README.md b/README.md
index 7b262d4..91935b6 100644
--- a/README.md
+++ b/README.md
@@ -44,7 +44,12 @@ Alternatively, you may explicitly use "--user", "--api-key", and
 `--site` in our examples, which is especially useful when testing.  If
 you are running several bots which share a home directory, we
 recommend using `--config` to specify the path to the `zuliprc` file
-for a specific bot.
+for a specific bot.  Finally, you can control the defaults for all of
+these variables using the environment variables `ZULIP_CONFIG`,
+`ZULIP_API_KEY`, `ZULIP_EMAIL`, `ZULIP_SITE`, `ZULIP_CERT`,
+`ZULIP_CERT_KEY`, and `ZULIP_CERT_BUNDLE`.  Command-line options take
+precedence over environment variables take precedence over the config
+files.
 
 The command line equivalents for other configuration options are:
 
diff --git a/zulip/__init__.py b/zulip/__init__.py
index 488c045..27d6969 100644
--- a/zulip/__init__.py
+++ b/zulip/__init__.py
@@ -186,8 +186,25 @@ class Client(object):
         if client is None:
             client = _default_client()
 
+        # Fill values from Environment Variables if not available in Constructor
+        if config_file is None:
+            config_file = os.environ.get("ZULIP_CONFIG")
+        if api_key is None:
+            api_key = os.environ.get("ZULIP_API_KEY")
+        if email is None:
+            email = os.environ.get("ZULIP_EMAIL")
+        if site is None:
+            site = os.environ.get("ZULIP_SITE")
+        if client_cert is None:
+            client_cert = os.environ.get("ZULIP_CERT")
+        if client_cert_key is None:
+            client_cert_key = os.environ.get("ZULIP_CERT_KEY")
+        if cert_bundle is None:
+            cert_bundle = os.environ.get("ZULIP_CERT_BUNDLE")
+
         if config_file is None:
             config_file = get_default_config_filename()
+
         if os.path.exists(config_file):
             config = SafeConfigParser()
             with open(config_file, 'r') as f: