Poly(ethylene succinate)/SiO₂ nanocomposites were prepared in situ with different SiO₂ contents. ¹³C NMR spectra revealed that the hydroxyl end groups of poly(ethylene succinate) could form covalent bonds with the surface silanol groups of SiO₂. These interactions had a significant positive effect on the molecular weight and mechanical properties of the nanocomposites. TEM revealed homogeneous dispersion of the nanoparticles, with some aggregates appearing at higher concentrations. Crystallization under isothermal and non-isothermal conditions was extensively studied. The nanoparticles acted as a nucleating agent and the nucleation activity was calculated for non-isothermal melt- and cold-crystallization. Activation energy of non-isothermal cold-crystallization was estimated using the isoconversional method of Friedman. Moreover, crystallization kinetics were analysed and spherulitic morphology also examined. The enzymatic hydrolysis rate of the nanocomposites was slowed down by the incorporation of the inorganic nanoparticles, attributed to the smaller available biodegradable surface and the existence of branched and crosslinked macromolecules.