A method and system for supporting Internet Protocol (IP) mobility of a Mobile Node (MN) in a mobile communication system. In the mobile communication system supporting Mobile IP (MIP) and Session Initiation Protocol (SIP), MIP location registration is performed in a Home Agent (HA) through a first FA (Foreign Agent) of a first foreign network in which the MN is located. When the MN receives a SIP invite message from a Correspondent Node (CN), it sends, to the CN, a SIP response OK message in which a home address of the MN is recorded. The CN sends a packet to the home address of the MN in a state in which a SIP call of the MN is established. The number of signaling messages and a delay time associated with a handover can be reduced, because the CN sends packets only to the home address of the MN regardless of a changed location of the MN.