Researching for new biomaterials intended for drug delivery systems has considerably intensified in recent years. There is an increasing interest in PBS (poly[butylene succinate]) and its copolymers as biomaterials due to the possibility of synthesis of the PBS from a renewable source. Among these copolymers, PBS‐PEG (poly[butylene succinate‐co‐polyethylene glycol]) is studied for materials that have shape memory and are biodegradable. However, to date, no research into the use of PBS‐PEG to prepare microspheres for drugs release has been reported. Herein, PBS‐PEGs with three PEG with different chain′s length were synthesized by polycondensation reaction and characterized by means of SEC, FTIR, DSC, TGA, and DRX. Naproxen loaded microspheres were prepared by an oil‐in‐water (o/w) single emulsion technique. The drug release was followed by UV‐Vis. The presence of PEG had a marked effect on the in vitro release profiles. The mathematical models employed show that the fundamental mechanism of release is diffusion when PEG is present in the polymer matrix of the particle.