Abstract: A system and method for synchronizing Broadcast/Multicast Service (BCMCS) traffic in a mobile communication system connected to a BCMCS server. A Packet Data Service Node (PDSN) receives a BCMCS content frame from the BCMCS server, and transmits a corresponding Generic Routing Encapsulation (GRE) packet BCMCS content frame, including a sequence number and a timestamp value indicating when the GRE packet BCMCS content frame is transmitted, to Packet Control Functions (PCF) connected downstream of the PDSN. Each of the PCFs determines whether the GRE packet BCMCS content frame received from the PDSN is valid, based on the sequence number included therein. If the GRE packet BCMCS content frame is valid, the PCF transmits the frame to its lower nodes connected downstream of the PCF, while synchronizing the frame transmission, based on the timestamp value included in the frame.