In this letter, we have presented an architecture and CoMP protocol for reliable mobility management mechanism in IoT environments. We extend the IETF CoAP protocol for achieving the reliability in IoT mobility management. In addition, we introduce the binding and holding mode to prevent the loss of signaling message during handover operation by extending the CoAP protocol. The mathematical analysis of the handover delay of CoMP is given. The performance evaluation shows that CoMP can effectively support the reliable mobility management.