A display device and a method for driving a backlight thereof are provided. The display device includes a signal generator configured to generate a first PWM (Pulse Width Modulation) signal and a second PWM signal, a low current driver configured to generate first output current using the first PWM signal, a high current driver configured to generate second output current using the second PWM signal, and a backlight configured to be driven by at least one of the first output current generated by the low current driver and the second output current generated by the high current driver. Accordingly, the display device can control the brightness of the backlight with an extended resolution which is higher than the resolution that can be output from the existing backlight.