The modification of polypropylene films (PP) was performed by radiation-induced graft polymerization of thermosensitive poly(N-isopropylacrylamide) (PNIPAAm). Graft polymerization was obtained by pre-irradiation method with doses from 10 to 200 kGy, at different monomer concentration, temperature, reaction time and dose rate; by using gamma rays from Co-60 source at room temperature. Grafting was confirmed by infrared (FTIR-ATR), and the structure of the grafted films was investigated by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS); low critical solution temperature (LCST) of the films was measured by water absorption and water contact angle.