[Object] To provide lubricating thermoplastic resin compositions that can give formed articles exhibiting excellent lubricating properties and surface appearance and maintaining the lubricating properties permanently. [Solution] The lubricating thermoplastic resin composition includes an acid-modified copolymer (A) of a monomer mixture including an aromatic vinyl and a vinyl cyanide, the copolymer having a carboxyl group in the molecular chain, and a functionalized lubricant (B) having, in the molecule, a functional group (B1) capable of reacting with the carboxyl group and a lubricating segment (B2) having lubricating properties. The composition may further include a graft copolymer (C) and/or an additional thermoplastic resin (D) other than the acid-modified copolymer (A).