diff --git a/include/mqtt_client.h b/include/mqtt_client.h
index 203bdab..192f5d0 100644
--- a/include/mqtt_client.h
+++ b/include/mqtt_client.h
@@ -348,6 +348,14 @@ esp_err_t esp_mqtt_set_config(esp_mqtt_client_handle_t client, const esp_mqtt_cl
  */
 esp_err_t esp_mqtt_client_register_event(esp_mqtt_client_handle_t client, esp_mqtt_event_id_t event, esp_event_handler_t event_handler, void* event_handler_arg);
 
+/**
+ * @brief Get outbox size
+ *
+ * @param client            mqtt client handle
+ * @return outbox size
+ */
+int esp_mqtt_client_get_outbox_size(esp_mqtt_client_handle_t client);
+
 #ifdef __cplusplus
 }
 #endif //__cplusplus
diff --git a/mqtt_client.c b/mqtt_client.c
index fed7e7b..7dcd3d5 100644
--- a/mqtt_client.c
+++ b/mqtt_client.c
@@ -1757,3 +1757,22 @@ static void esp_mqtt_client_dispatch_tls_error(esp_mqtt_client_handle_t client)
 #endif
         esp_mqtt_dispatch_event_with_msgid(client);
 }
+
+int esp_mqtt_client_get_outbox_size(esp_mqtt_client_handle_t client)
+{
+    int outbox_size = 0;
+
+    if (client == NULL) {
+        return 0;
+    }
+
+    MQTT_API_LOCK(client);
+
+    if (client->outbox) {
+        outbox_size = outbox_get_size(client->outbox);
+    }
+
+    MQTT_API_UNLOCK(client);
+
+    return outbox_size;
+}