Disclosed are a robot cleaner and a method for controlling the same, capable of controlling a travelling or cleaning pattern of a robot cleaner in accordance with extension and retraction operations of an auxiliary cleaning tool to perform an efficient cleaning operation. The robot cleaner includes a plurality of auxiliary cleaning units mounted to a bottom of the robot cleaner such that the auxiliary cleaning units are extendable and retractable, an obstacle sensor to sense an obstacle in a cleaning region of the robot cleaner, and a control unit to extend the auxiliary cleaning units while travelling in a wall tracing manner along the periphery of the cleaning region, and to retract the auxiliary cleaning units while the robot cleaner travels in an inner portion of the cleaning region when traveling of the periphery of the cleaning region is finished.