A backlight assembly includes a light source, a circuit board on which the light source is disposed, a light guide plate in which light emitted from the light source is incident on one surface and is emitted to the other surface, a bottom case configured to accommodate the light guide plate, and a wavelength conversion unit between the light source and the light guide plate. The wavelength conversion unit includes a frame having an opening, the rectangular frame including a top frame, a bottom frame and side frames extending substantially perpendicular to the top frame and the bottom frame, and connecting the top frame and the bottom frame.