A mobile terminal and a method of controlling an operation thereof are disclosed. In the method of controlling the operation of the mobile terminal, the mobile terminal is communicatively with a head mounted display for displaying an augmented reality (AR) screen obtained by combining a virtual image with a real environment. If image data acquired through a camera is analyzed and a predetermined gesture input is detected, the head mounted display is controlled such that a display change corresponding to the detected gesture input is displayed on the AR screen. In a state of displaying the AR screen through the head mounted display, various operations related to the mobile terminal can be controlled according to the predetermined gesture input.