An aromatic vinyl copolymer is a polymer of a reaction mixture including: an aromatic vinyl compound; a vinyl cyanide compound; a first silicone compound having a weight average molecular weight of about 150 g/mol to less than about 6,000 g/mol and including at least two unsaturated reactive groups; and a second silicone compound having a weight average molecular weight of about 6,000 g/mol to about 100,000 g/mol and including at least two unsaturated reactive groups. A thermoplastic resin composition including the aromatic vinyl copolymer can exhibit excellent matting properties, impact resistance, and balance therebetween.