A versatile and non destructive technique for a chemical modification by grafting N-vinylcaprolactam (VCL) monomer on the polylactic (PLA) film surface is described. The film substrate is treated with a VCL solution, hexane and benzophenone (BP), the latest promotes the photo initiation. Grafting percentage is derived by a gravimetric method and the success in grafting is evaluated by contact angle technique, UV and ATR-FTIR analysis. The influence of the photoinitiator concentration is evaluated by the polymerization rate (Cp), grafting percentage (Cg) and grafting efficiency (Eg). The modified surface shows higher level of humectation or hydrophilicity, confirming successful surface functionalization of the polylactic acid film.