A thermoplastic resin composition for automotive interior materials including 20% to 42% by weight of a polyester resin (A); 20% to 32% by weight of a vinyl cyanide compound-conjugated diene compound-aromatic vinyl compound graft copolymer (B); and 30% to 48% by weight of an aromatic vinyl compound-vinyl cyanide compound copolymer (C), a method of preparing the thermoplastic resin composition, and a molded article including the thermoplastic resin composition. The thermoplastic resin composition has excellent environmental stress cracking (ESC), processability, injection moldability, injection stability, and economics while maintaining mechanical properties, thermal stability, and friction noise resistance equal or superior to those of conventional heat-resistant ABS resin compositions.