Abstract: A mouthguard composition is disclosed, containing (a) from 40 to 80% by weight of a styrene block copolymer, (b) from 20 to 60% by weight of an alicyclic saturated hydrocarbon resin and/or an ester gum, and (c) from 0.1 to 10% by weight of an organopolysiloxane in which at least one of organic groups directly bound to the silicon atom in one molecule thereof is a phenyl group, a methylstyryl group, or an alkyl group having from 7 to 30 carbon atoms. The mouthguard composition is high in durability and impact absorption and is free from sticking to gypsum model or hands and fingers at the time of preparation and adjustment works.