This research supports a practical, cost-effective method for manufacturing, thermally stable polymer composites. A thermogravimetric study was conducted on polycarbonate (PC) and PC/graphene nanoplatelets (GNPs) composites in nitrogen and air atmospheres. In the presence of nitrogen, PC decomposed in a one-step manner, but in the presence of air, three-step deterioration was observed. Furthermore, pure graphene nanoplatelets degraded in three steps in air, associated with a moderate deterioration in N2, as received. The inclusion of platelet-like graphene aided to produce a physical hindrance outcome, postponing the release of volatile chemicals created throughout breakdown, which enhanced the thermal strength of the composites. © 2023 American Institute of Physics Inc.. All rights reserved.