Since the ZigBee mesh routing algorithm is similar to AODV based on flooding, the networks suffer from the scalability problem as the number of nodes or the data traffic increases. Thus, for low-rate ZigBee mesh networks it is necessary to design an effective routing protocol to take the scalability into account. In this paper, we propose a ZigBee mesh routing protocol based on Cluster Label (ZiCL). As ZiCL hierarchically divides a ZigBee-enabled network into one or more logical clusters, when a node starts route discovery procedure, it encourages nodes with the same Cluster Label to share the routing information. This results in fewer route discoveries, and hence effectively relieves the number of potential control traffic required to establish a shortest path between nodes. Simulation results show that ZiCL helps to reduce routing overhead and improve performance of ZigBee mesh networks.