The physicochemical properties of aceclofenac nanocapsules, prepared by interfacial precipitation of poly-e-caprolactone at the oil/water interface, have been studied. A Central Composite Design was used to investigate the influence of polymerization adjuvants on these properties on the elaboration of aceclofenac-loaded poly-e-caprolactone nanocapsules. In this way, the effect of polymer, oil and drug concentrations in organic phase on the size and encapsulation efficiency has been analyzed. The optimized nanocapsule formulation leads to use an initial concentration of drug (aceclofenac) of 0.8 mg/ml and 0.6% of oil (Miglyol 812), being the polymer and surfactant concentrations previously fixed.