AbstractThe design of polymeric nanoparticles has gained significant attention for drug delivery and controlled release applications. Biocompatible and degradable polyesters have emerged as promising materials for this purpose. However, achieving precise control over the size of nanoparticles (NPs) is crucial to ensure selective delivery and avoid clearance by the reticuloendothelial system. This study investigates the impact of external parameters, including polymer concentration, sonication amplitude, and sonication time, on the preparation of polymeric NPs using starch butyrate (SB) via the single emulsification‐solvent evaporation (SE‐SE) technique with ultrasound assistance. Employing a Box–Behnken method, this study optimizes the conditions for nanoformulation, obtaining response surfaces that reveal the effects of these parameters on particle size. These findings highlight that sonication time is the most influential parameter, followed by sonication amplitude and polymer concentration. By utilizing the statistical model, this study predicts and controls the variables to achieve particle diameters ranging from 152 to 346 nm. The optimal conditions for NPs preparation involve a polymer concentration of 1 mg mL−1, 40% sonication amplitude, and a 30‐min sonication time, resulting in particle sizes of 142 nm. Furthermore, this model demonstrates the capability to develop nanoformulations with excellent size homogeneity, enhancing their attractiveness and efficacy in drug delivery applications.