To provide a mouth guard composition which hardly generates plastic deformation and which is high in fluidity during the formation after heating and softening and superior in fitness, and which even after repeated use of a mouth guard prepared therefrom, is free from sticking with respect to its surface and does not cause an offensive smell. The mouth guard composition is constituted of 3998% by weight of a styrene block copolymer; 160% by weight of at least one thermoplastic resin selected from the group consisting of an alicyclic saturated hydrocarbon-based resin, a terpene resin, and an aliphatic petroleum resin; and 140% by weight of at least one wax selected from the group consisting of a mineral wax, a synthetic wax, a vegetable-based wax, and an animal-based wax.