A backlight assembly includes a light source, a light-guide plate, a mold frame and a bottom chassis. The mold frame includes a first bottom portion, a protrusion on a first surface of the first bottom portion and a first sidewall portion on a second surface of the first bottom portion opposite to the first surface of the first bottom portion and facing the light guide plate. The bottom chassis includes a second bottom portion having a hole to receive the protrusion of the first bottom portion, and a second sidewall portion facing the light guide plate. A cross sectional area of a first opening of the hole corresponding to an inner surface of the bottom chassis and contacting the first surface of mold frame is different than a cross sectional area of a second opening of the hole corresponding to an outer surface of the bottom chassis.