The present invention relates to a matrix copolymer including a cellulose nanocrystal derivative, an alkyl (meth)acrylate-based monomer unit, an aromatic vinyl-based monomer unit, and a vinyl cyan-based monomer unit; a graft copolymer including a cellulose nanocrystal derivative, a conjugated diene-based polymer, an alkyl (meth)acrylate-based monomer unit, an aromatic vinyl-based monomer unit, and a vinyl cyan-based monomer unit; and a thermoplastic resin composition including at least one thereof. In accordance with the present invention, provided is a thermoplastic resin composition having improved processability, impact strength, tensile strength and chemical resistance while maintaining transparency.