An apparatus and a method for reducing battery consumption of a mobile terminal are provided. More particularly, an apparatus and a method for reducing battery consumption by allowing a mobile terminal to perform a wakeup process by expiration or update of a timer which coincides with a paging period in order to reduce battery consumption. The controller reduces a frequency of waking up from a sleep mode by matching a wakeup time set by a timer to a paging period with a certain condition is met.