A method and an apparatus for transmitting a signal at a cooperative user equipment in a wireless communication system supporting client cooperative communication is provided. The method includes: receiving one or more packets configured in predetermined units from a source user equipment; configuring a data burst respective to the source user equipment based on the predetermined units by including the one or more packets in the data burst based on a priority level; and transmitting the data burst to a base station. Here, the one or more packets are configured in one of service data units (SDUs) and protocol data units (PDUs), and the priority level is same as a priority level used by the source user equipment.