Embodiments herein achieve a method for handling registration and session management in a wireless communication system. The method includes registering, by a User Equipment (UE), with a first core network entity over a 3GPP access network and a non-3GPP access network. Further, the method includes triggering, by the UE, a registration procedure to a second core network over the 3GPP access network when a periodic timer of the UE expires in an OOS state. Further, the method includes receiving, by the UE, a non-access stratum (NAS) message, over the 3GPP access network, with an indication to register for the non-3GPP access network with the second core network entity. Further, the method includes reinitiating the registration procedure to register again for the non-3GPP access with the second core network entity through the non-3GPP access network.