Abstract: A cap blocker provides for the maintenance of the shape of a billed, baseball type cap, particularly the shape of the front of the cap above the bill. The device is preferably formed of a flat, planar sheet of sturdy, relatively stiff material, which material allows at least some flexibility to adapt to the curvature of the band of a cap or the like. A vinyl plastic sheet material may be used, as well as other suitable materials. The cap blocker is inserted into the band of a cap, between the band and the outer cap material, where it extends upward into the front of the cap above the bill to prevent the collapse or deformation of that area of the cap. The blocker may also include relief areas along the upper edge, allowing the upper edge to be folded inward to accommodate the compound curvature of the top of the cap. Ventilation holes may also be provided for additional wearer comfort.