Disclosed are a method and apparatus for determining a PDU session identity in a wireless communication system. A method for determining, by a session management function (SMF) node, a packet data network (PDU) session identity during handover of user equipment (UE) in a wireless communication system, may include receiving a request message for requesting the establishment of a PDU session for the UE from an access and mobility management function (AMF) node, wherein a handover for the UE from a first wireless communication system to a second wireless communication system has been determined, determining a PDU session identity for the PDU session established for the UE when the request message is received, and sending a response message including the determined PDU session identity to the AMF node in response to the request message.