A method of managing a keypad of a handheld electronic device comprises promoting a user whether a size of the keypad needs adjustment when the handheld electronic device is in a single hand operating mode. If the answer is yes, the handheld electronic device then detects a movement of a finger of the user on a touch screen thereof. When a movement of the finger along a diagonal direction of the keypad away from the keypad is detected, the size of the keypad is increased. When a movement of the finger alone the diagonal direction of the keypad toward the keypad is detected, the size of the keypad is decreased. When the movement of the finger is stopped and a “Done” button is pressed, the adjustment of the size of the keypad is completed, and the size of the keypad after adjustment is stored in a storage module.