BACKGROUND Poly(ethylene terephthalate) (PET) waste films were treated by cold plasma aminolysis to graft primary amino groups (‐NH2) and the surface biocompatibility of the polymer was improved. Aminated PET waste films were obtained by applying radiofrequency (RF) plasma treatment of either diethylenetriamine (DTA) or ethylenediamine (EDA). Aminolysis was applied during 5, 10 and 15 min at plasma power levels of 150, 175 and 200 W. RESULTS Water contact angle study revealed that the surface of PET waste films became more hydrophilic after plasma treatment, the contact angles decreased as exposure time or plasma power increased. Also, X‐ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) detected signals related to ‐NH2 functional groups at the surface of treated PET films. In relation to the biocompatibility properties of the aminated PET waste films, most of them, do not present hemolytic problems, but those treated with DTA at 150 W for 10 min (PET‐DTA/150 W‐10 min) showed the least hemolytic effect. On the other hand, it was proved that plasma treatment of PET waste films conferred a sterilization effect against Pseudomonas aeruginosa bacteria. CONCLUSIONS The biocompatible properties of PET were improved while the material was sterilized due to the ultraviolet radiation and free electrons generated during plasma treatment. These results suggest that aminated PET waste films have the potential to be used in biological or biomedical applications by taking advantage of ecofriendly technology such as cold plasma and the reuse of waste polymers such as PET from purified water bottles. © 2022 Society of Chemical Industry (SCI).