In the quest for better supercapacitor performance, materials with high energy storage, rapid charge transfer and excellent charge-discharge capabilities are crucial. However, improving energy density and optimizing electrode materials for supercapacitors remains a challenge. Within this perspective, we developed a novel aniline-derived polybenzoxazole-reduced graphene oxide composite (Mn3O4-pBOA-rGO) for supercapacitor applications. An electrode for supercapacitor applications was then fabricated using the synthesized composite. Various characterization techniques, such as X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy, were employed to analyze the structure of the material and cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge tests were performed to evaluate the supercapacitive performance. Remarkably, the Mn3O4-pBOA-rGO ternary nanocomposite-based electrode exhibited enhanced electrochemical performance achieving an energy density of 116 Wh kg−1 in a 1 M aqueous Na2SO4 electrolyte at a current density of 1 A g−1. In comparison, the Mn3O4-pBOA binary nanocomposite recorded an energy density of 25 Wh kg−1, while bare Mn3O4 yielded 10 Wh kg−1. The significantly improved electrochemical properties of the Mn3O4-pBOA-rGO composite present a promising and viable solution for supercapacitor applications.