An apparatus, method, and medium for sensing a slip in a mobile robot is provided. The apparatus for sensing a slip in a mobile robot includes a driving motor control unit to control a driving motor that rotates a plurality of driving wheels of the mobile robot, a first rotation sensor to sense a first rotation angle of the mobile robot by using the difference between traveling distances of the plurality of driving wheels, a second rotation sensor to sense a second rotation angle of the mobile robot by sensing a rotation of the mobile robot, and a slip-sensing unit to sense the slip of the mobile robot by comparing the first rotation angle with the second rotation angle. The driving motor control unit controls the driving motor to travel straight in a specified pattern.