The aim of this study was to develop a nano-emulsion of Sacha inchi oil for cosmetic application by the emulsion phase inversion (EPI) method. The influence of surfactant type and surfactant-to-oil ratio (SOR) on the particle size distributions of the nano-emulsion was studied. The results obtained showed that nano-emulsion droplet size and stability of nano-emulsions were varied considerably. The optimal nano-emulsion formulations were found to be in the range of 87.63 wt.% of water, 4.87 wt.% of oil, and 7.5 wt.% of surfactant mixture. The smallest size (41.50 ± 0.12 nm) and high zeta potential values (-30.42±0.22 mV) were obtained. [ABSTRACT FROM AUTHOR]