An object of the present invention is to obtain unsaturated polyester resin compositions for lamp reflectors and molded articles thereof, which have excellent coating properties in addition to excellent surface smoothness, dimensional accuracy, moldability, heat resistance and mechanical strength. The unsaturated polyester resin compositions comprise (a) an unsaturated polyester resin, (b) a diallyl phthalate monomer or prepolymer, (c) a radical polymeric unsaturated monomer other than the diallyl phthalate monomer, (d) a polystyrene and/or a styrene-vinyl acetate block copolymer, and (e) a styrene-diene block copolymer and/or hydrogenated or modified styrene-diene block copolymer. Further, the unsaturated polyester resin compositions comprise from 20 to 60 parts by weight of (b) and (c), and from 13 to 34 parts by weight of (d) and (e) based on 100 parts by weight of (a), (b), (c), (d) and (e), and the ratio by weight of (b) to (c) is 5:95 to 25:75, and the ratio by weight of (d) to (e) is 20:80 to 80:20.