An apparatus and method for updating a neighbor list in a mobile communication system are provided. The system includes a Mobile Station (MS), a second Base Station (BS), and a first BS. The MS stores first log information, performs a network entry process with the second BS, and generates and transmits second log information to the second BS. The second BS allocates a bandwidth to the MS, receives the second log information, determines if neighbor list update is required using the second log information and, if the neighbor list update is required, updates a neighbor list and transmits the updated neighbor list information to the previous BS.