Ursolic acid (UA) was nanoencapsulated in PLA nanoparticles. Release of UA from nanoparticles was slow, biphasic and diffusion-controlled. Antioxidant activity of UA was maintained after nanoencapsulation. PLA nanoparticles decreased the hemolytic activity of UA. Nanoparticles exhibited time/concentration dependent cytotoxicity over B16-F10 cells.