Provided is a thermoplastic resin composition which includes: a first graft copolymer including a C4 to C10 alkyl (meth)acrylate-based monomer unit, an aromatic vinyl-based monomer unit, and a vinyl cyan-based monomer unit; a second graft copolymer including a C4 to C10 alkyl (meth)acrylate-based monomer unit, an aromatic vinyl-based monomer unit, and a vinyl cyan-based monomer unit; and a first styrene-based copolymer being a copolymer of a monomer mixture including a C1 to C3 alkyl-substituted styrene-based monomer, a vinyl cyan-based monomer, and a C1 to C3 alkyl (meth)acrylate-based monomer, wherein the first graft copolymer and the second graft copolymer have cores having mutually different average particle diameters. The thermoplastic resin composition is excellent in colorability, weather resistance, tensile strength, flexural strength, and impact strength.