Disclosed is a thermoplastic resin composition comprising (A) a graft copolymer obtained by emulsion-graft-polymerizing 0 to 20% by weight of an acrylic monomer and 0 to 60% by weight of an aromatic vinyl monomer in the presence of 40 to 80% by weight (as solids) of a diene type rubber polymer latex containing at least 50% by weight of a diene type rubber polymer having a weight average particle diameter of at least 0.3 .mu.m, and (B) a copolymer of an .alpha.,.beta.-unsaturated cyclic anhydride and an aromatic vinyl compound. The thermoplastic resin composition has a high heat resistance and impact resistance.