Core-shell copolymer, method for preparing the same and thermoplastic resin composition including the same

A core-shell copolymer, a method of making the same, and a thermoplastic resin composition including the same are disclosed herein. In some embodiments, a core-shell copolymer includes a core and a shell surrounding the core, the core includes a conjugated diene-based monomer-derived repeating unit and a phosphate-based cross-linking agent-derived cross-linking part represented by Formula 1, and the shell includes a first alkyl (meth)acrylate monomer-derived repeating unit, a second alkyl (meth)acrylate monomer-derived repeating unit, and a sulfonate-based ionic monomer-derived repeating unit represented by Formula 2. The core is 68 parts to 92 parts and the shell is 8 parts to 32 parts, based on 100 parts of the core-shell copolymer, the core has a swell index of 2.7 to 10.9, the shell includes 1 wt % to 16 wt % of the sulfonate-based ionic monomer-derived repeating unit, and the shell has a weight average molecular weight of 105,000 g/mol to 645,000 g/mol.