Stimuli-responsive unimer nanoparticles (NPs) composed of hydrophobized poly(gamma-glutamic acid) were successfully prepared by a combination of hydrophobic interactions and disulfide bonds. The formation of hydrophobic associations and the existence of disulfide bonds were confirmed by UV spectroscopy and by treatment with dithiothreitol, respectively. Moreover, the release of hydrophobic drugs in response to a reducing agent was observed when compared to nonstimulus unimer NPs. These 10 nm-sized unimer NPs will be useful as reduction-responsive carriers.