Provided is a backlight assembly including: a light source which generates and emits light; a light leakage preventing member including a first horizontal portion and a first vertical portion; a light guide plate including a light input surface and a light output surface; an optical sheet disposed on the light output surface of the light guide plate; and a bottom chassis configured to receive the light source, the light leakage preventing member and the light guide plate therein, in which the light source is disposed at a side of the light guide plate, the first vertical portion of the light leakage preventing member is attached to a rear surface of the light source, and the first horizontal portion is positioned above the light source to overlap a portion of the light output surface of the light guide plate.