A mobile device and a method for providing a tethering service via a security mode and a list of preferred mobile devices are provided. The method includes determining, when the mobile device receives a connection request from a client mobile device, a number of client mobile devices that are currently connected to the mobile device, determining, when the number of connected client mobile devices is less than a preset maximum connection number, the number of created Basic Service Sets (BSSs), determining, when the number of BSSs is less than a preset maximum creation number, the identification-information regarding the client mobile device that requested connection, and providing a tethering service to the client mobile device according to the determined identification-information.