Graphene, which is a layer of carbon atoms in a hexagonal lattice, has been reported to have excellent mechanical, electrical, thermal, and gas barrier properties. One of the most widely used applications of graphene is grapheme-polymer composites, which are one of the most promising solutions, since highly functional materials can be produced with a small amount graphene flakes incorporated in a lightweight polymer matrix. Graphene-polymer composites have been investigated for various types of applications such as thermal interface materials, electromagnetic interference shielding materials, gas sensor materials, and gas barrier materials.