diff --git a/homeassistant/components/mqtt/__init__.py b/homeassistant/components/mqtt/__init__.py
index 09655ababda..5898b1918a2 100644
--- a/homeassistant/components/mqtt/__init__.py
+++ b/homeassistant/components/mqtt/__init__.py
@@ -10,6 +10,7 @@ import os
 import ssl
 import time
 from typing import Any, Callable, List, Optional, Union
+import uuid
 
 import attr
 import certifi
@@ -711,9 +712,10 @@ class MQTT:
 
         client_id = self.conf.get(CONF_CLIENT_ID)
         if client_id is None:
-            self._mqttc = mqtt.Client(protocol=proto)
-        else:
-            self._mqttc = mqtt.Client(client_id, protocol=proto)
+            # PAHO MQTT relies on the MQTT server to generate random client IDs.
+            # However, that feature is not mandatory so we generate our own.
+            client_id = mqtt.base62(uuid.uuid4().int, padding=22)
+        self._mqttc = mqtt.Client(client_id, protocol=proto)
 
         # Enable logging
         self._mqttc.enable_logger()