Embodiments herein provide a method for performing multiple authentications within a service registration procedure. The method includes sending, by a User Equipment (UE) a REGISTER request message to an IP Multimedia Subsystem (IMS) server. Further, the method includes receiving, an IMS authentication challenge from the IMS server, where the IMS authentication challenge includes an IMS authentication parameter and a MCPTT authentication challenge. Further, the method includes verifying, at the UE, the IMS authentication challenge. Further, the method includes generating, at the UE, a REGISTER response message. Further, the method includes sending, a REGISTER response message to the IMS server, where the REGISTER response message includes an IMS authentication response to authenticate UE at the IMS server and a MCPTT authentication response to authenticate the UE at the MCPTT server.