A method of performing Dual Transfer Mode (DTM) handover by a mobile station (MS) in a wireless mobile communication system is disclosed. More specifically, the MS receives information of neighbor cells, wherein the information is a list of neighbor cells whose signal strengths the MS should measure and transmits a message including results of the measured neighbor cells. Furthermore, the MS receives a message from a network, wherein the message is a DTM Handover Command message which instructs the MS to perform a DTM handover procedure with one of the neighbor cells. Lastly, the MS performs the DTM handover procedure.