© 2020 Elsevier B.V. Tailoring surface hydrophilicity on polyethylene terephthalate (PET) by a radio frequency (RF) atmospheric pressure plasma jet (APPJ) for grafting biomaterials was investigated in this study. Two thermally responsive biomaterials of hydrophilic non-ionic surfactant of polyoxyethylene polymer and hydroxypropyl cellulose were used, while hydroxyethylmethacrylate (HEMA) was applied as the carrier for drug release. As applying the RF power in an APPJ system, PET substrates represented a tendency from an originally hydrophobic surface to a hydrophilic one, while apparent damaged areas were observed as the RF power exceeded 200 W. APPJ-induced polar functional groups onto PET surface without serious etching were most likely to improve the surface hydrophilicity for further grafting biomaterials. The grafted polyoxyethylene polymer on APPJ-treated PET substrates exhibited a surface change from opaque into transparent as the ambient temperature exceeded lower critical solution temperature of 37°C, while hydroxypropyl cellulose displayed a change from transparent into milky white as the temperature over 55°C. For the drug release behavior of aspirin on APPJ-treated PET substrates, the cumulative release rate of aspirin entrapped substrate for 3 h was 22%. Our results suggest that tailoring surface hydrophilicity of PET substrates without surface etching by 100W-APPJ process possessed a higher surface energy with a higher polar interaction, resulting in a good bonding with the grafted biomaterials.