Plasma surface modifications of polymer scaffolds using biomolecules such as oxygen, nitrogen, and other active grafting molecules have been studied to enhance biological responses such as cell attachment, spreading, and proliferation. According to the reports, nitrogen grafting requires corrosive or mixture gas environment, or post treatment. This study aimed to evaluate a simple atmospheric pressure plasma surface modification in order to graft nitrogen derivatives and to promote biological responses. In this study, a polycarprolactone (PCL) film was modified within 10 min by argon atmospheric pressure discharge (Ar-APGD). Excited argon atoms, nitrogen atoms, oxygen atoms, and hydroxyl functional groups were observed from the optical emission spectra of the discharge. Decreased carbonyl functional groups and ether functional groups were observed; notably, immobilized nitrogen was observed on the PCL surface after the Ar-APGD treatment. Promoted neonatal Human Dermal Fibroblast (nHDF) growth patterns were observed on the Ar-APGD-treated surface.