In this study, a novel simple and fast method was developed of immobilizing a natural polysaccharide (chitosan) on a polylactide (PLA) surface. In order to overcome the lack of surface adhesion between the chitosan and the PLA due to incompatibility issues, atmospheric pressure plasma was used. The plasma activation was able to modify the PLA surface by generating surface chemistry proper for stabilizing the chitosan layer. The activation of the surface was monitored through water contact angle (WCA) measurements and X-ray photoelectron spectroscopy (XPS). Indeed, the introduction of new functionalities lowers the hydrophobicity of the PLA surface allowing an effective spreading and immobilization of the chitosan layer. The presence of chitosan on the polyester's surface was proven by Fourier transform infrared spectroscopy (FTIR).