The present disclosure relates to transmitting a response message in wireless communications. According to an embodiment of the present disclosure, a method performed by a wireless device served by a master node (MN) and a secondary node (SN) in a dual connectivity (DC) in a wireless communication system comprises: receiving, from the MN via a signalling radio bearer 1 (SRB1), a conditional primary secondary cell change (CPC) command related to a radio resource control (RRC) reconfiguration message of which a RRC transaction identifier (ID) is set; performing a CPC execution based on that a CPC condition in the CPC command is satisfied; and transmitting, to the MN, an RRC message of which no RRC transaction ID is set based on the CPC execution, wherein the RRC message comprises a RRC reconfiguration complete message of which the RRC transaction ID is set.