Polymeric nanoparticles have attracted growing attention because of their unique properties and extensive application. In this study, polycaprolactone (PCL) nanoparticles were prepared via double emulsion solvent evaporation-like process using power ultrasound, and the effects of various process parameters on particle size, zeta potential, and morphology were investigated and optimized. Nanoparticles (NPs) were prepared by two-step emulsification process. In the first step, the inner aqueous phase (W₁) was homogenized with organic phase (PCL in dichloromethane) to obtain primary emulsion. In the second step, the primary emulsion was emulsified with outer aqueous phase (W₂) containing polyvinyl alcohol (PVA) as stabilizer using power ultrasound, followed by evaporation of solvent which resulted in a particulate suspension at the end. Effects of various parameters like ultrasound exposure time and amplitude, outer aqueous phase volume, PVA concentration, and PCL content were investigated. It has been shown that, by increasing ultrasound exposure time, amplitude, and outer aqueous phase volume, the particle size decreases. Additionally, particle size was also related to amount of PCL and PVA concentration. Spherical NPs with smooth surfaces were observed by scanning electron microscopy (SEM).