Polystyrene (PSt) was grafted onto a thermoplastic polyurethane (TPU) through a combination of atom transfer radical polymerization and "grafting to" techniques to afford a TPU-g-PSt copolymer. The chemical structures of the synthesized polymers were characterized using Fourier transform infrared and proton nuclear magnetic resonance spectroscopies. The polymer/clay nanocomposite of the resultant TPU-g-PSt copolymer was fabricated through a solution intercalation approach. The powder X-ray diffraction and transmission electron microscopy studies revealed an intercalated structure for the fabricated TPU-g-PSt/clay nanocomposite. According to thermal property studies' results, the fabricated TPU-g-PSt/clay nanocomposite exhibited higher thermal stability upon the addition of only a small amount (5 wt%) of organoclay.