To provide a light source device capable of irradiating a liquid crystal display module with light at uniform luminance and a display device including the light source device. A light source device has a rear vessel a front cover, a light source substrate, a plurality of light-emitting diodes, and a light-diffusing plate. The front cover is located over and overlaps the rear vessel. The light source substrate, the plurality of light-emitting diodes, and the light-diffusing plate are accommodated between the rear vessel and the front cover. The plurality of light-emitting diodes is located over the light source substrate. The light-diffusing plate is located over, overlaps, and is spaced away from the plurality of light-emitting diodes. The rear vessel and the front cover each have a bottom plate and a side plate integrated with the bottom plate. In at least one of the rear vessel and the front cover, a portion of the side plate is bent to form a protruding portion overlapping the bottom plate. The light-diffusing plate is located over and overlaps the protruding portion.