In this article, polyhedral oligomeric silsesquioxane (POSS)-containing aliphatic polyester composites were synthesized using condensation polymerization. Firstly, a series of polyesters have been prepared from malonic acid, succinic acid, adipic acid, sebacic acid (diacids), and 1,4-butanediol. On the other step of this study, polyester composites were synthesized between 1,2-propanediolisobutyl POSS (POSS-Diol) and diacid. For comparison, the same reaction was repeated in the presence of 1,4-butanediol, POSS-Diol, and diacids. The resulting samples were characterized by proton nuclear magnetic resonance, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy. Thermal behaviors of molecules were analyzed using thermogravimetry (TG) analysis. Molecular weights of synthesized polymers were determined with gel permeation chromatography (GPC). The XPS results indicate that the POSS hybrid molecule was successfully incorporated into the polyester structure. The characteristic binding energies of organic silicium atoms and Si-O were observed at 102 eV and 104 eV, respectively. According to the results from GPC, POSS-containing polyester composites (POSS-Diol + diacid + 1,4-butanediol) have higher molecular weight. The number-average molecular weights (M-n) of polyester composites b(1),b(2),b(3), and b(4) are found to be 6800 g/mol, 7050 g/mol, 7200 g/mol, and 7250 g/mol, respectively. TG results show that the resistance to thermal degradation of POSS-containing polymer bonds is not strong as expected. The results support that the synthesized POSS-based polyesters can be used as high-performance commercial polymers.