In this study, it has been demonstrated that polyhedral oligomeric silsesquioxane (POSS) based graphene-polycaprolactone nanocomposites (POSS-G-PCL) were successfully prepared by using ring opening polymerization method. For this purpose, first, graphene-POSS composite (GP) was synthesized with graphene oxide and aminopropyllsobutyl POSS (POSS-NH2). Second, POSS containing graphene-polycaprolactone composite (PCL-G-POSS) was synthesized by using e-caprolactone, graphene-POSS, and Tin(II) octanoate as initiator in DMF at 110 degrees C. This reaction was repeated without of solvent (PCL-G-POSS in bulk) and by using different amount of caprolactone (PCL*-G-POSS). The synthesized composites and polymers were characterized by nuclear magnetic resonance (H-1 NMR), gel permeation chromatography (GPC), and fourier transform infrared spectroscopy (FTIR). Thermal behaviors of molecules were analyzed by thermogravimetry (TG). The surface morphologies of composites were analyzed by scanning electron microscope (SEM). The results of TG and GPC analyses showed that the thermal stability and molecular weight of the composites were increased with the addition of POSS.