Provided are embodiments of an optical sheet and a backlight assembly having the optical sheet. The optical sheet can include a body, a plurality of protrusions, and a plurality of embossed portions. The body can form a substrate. One surface of the body can be provided in a planar shape, and the other surface of the body can include the plurality of protrusions, where the protrusions have a triangular shaped cross-section. Each of the protrusions can be configured with the plurality of embossed, which may be formed by a microlens pattern.