The approach of using micro-emulsions chemical method has demonstrated impressive success for the formation of nanoparticles specialized for drug delivery. The purpose of this study was to investigate the influence of manipulating five distinct formation factors during the micro-emulsion preparation method on the size of nanoparticles produced. These factors constituted the stirring speed, blending time, the type of surfactant, homogenization and the Poly (ethylene-co-vinyl acetate) (PEVA) concentration. Information on the particles sizes and their distribution were obtained and analyzed using ZetaSizerNanoZS. The results revealed that small sizes and narrow/uniform particle size distributions were obtained at lower polymer (0.2 % w/v) concentrations, a reduced stirring speed (2000rpm) and with the presence of polysorbate 80 surfactant. In contrast, higher polymer (1 % w/v) concentrations and stirring speed (6000rpm), in the absence of surfactant and homogenization, yielded larger particles with a multi-modal size distribution profile (PDI:0.749). These results also clearly revealed that the particle size was significantly affected by the combination of parameters here explored, and that on-demand nanoparticles may be produced using optimized micro-emulsion parameters to meet several potential applications.