A washing machine that calculates a temperature of a balancer to effectively control a motor and a method of controlling the washing machine are provided. The washing machine comprises a rotatable drum that receives laundry, a motor that rotates the drum, a balancer that is connected to the drum, the balancer changing a center of gravity of the drum, and a controller that rotates the motor at a constant rotational speed and then calculates a temperature of the balancer based on a period of a variation in rotational speed of the motor.
