A pair of cap-mounted sun glasses is provided, which contains a glasses member, two clipping members, and two joint members. The glasses member has seat elements on the top rim for receiving the spherical elements at an end of the joint members. The joint members therefore can rotate around their spherical elements. As such, after the pair of sun glasses is mounted below the brim of a cap, the glasses member can be flipped up or down manually. At the other end of the joint members, there is a bolt element for fitting inside the slot opening of the clipping member having a hook portion for clipping the edge of the brim. As such, the clipping member can be extended outward to fit on a wider brim or withdrawn inward to fit on a narrower brim.