Display omitted •Ternary nanohybrid based on rGO, NiMn2O4, and polyaniline (GNMOP) was fabricated by a three-step green process for supercapacitor applications.•GNMOP exhibited high specific capacitance of 757Fg−1 at 1Ag−1 of current density.•GNMOP showed 93% of specific capacitance retention after 2000 cycles.•GNMOP also exhibited high energy density of up to 70Whkg−1 and high power density of up to 12000Wkg−1. This paper reports a novel porous ternary nanohybrid based on NiMn2O4, reduced graphene oxide, and polyaniline (GNMOP) as a superior supercapacitor electrode material. GNMOP was fabricated using a hydrothermal-assisted thermal annealing method, followed by the conductive wrapping of polyaniline through in-situ polymerization. The structure and morphology of the ternary nanohybrid were characterized by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). FTIR, XRD, and XPS confirmed the formation of ternary nanohybrid. SEM and Brunauer–Emmett–Teller (BET) measurement revealed the porous nature of GNMOP, whereas HRTEM analysis demonstrated the wrapping of conducting polyaniline (PANI) on binary composite. Such PANI wrapping enhanced the electrochemical performance of the binary nanocomposite. A specific capacitance of 757Fg−1 was achieved for GNMOP at a current density of 1Ag−1, which is much higher than that of the binary nanocomposite and mixed transition metal oxide. In addition, GNMOP exhibited a maximum energy density of 70Whkg−1 and high capacitance retention of ∼93% after 2000 cycles. These outstanding electrochemical performances of GNMOP can be attributed to the proper wrapping of conducting polymer and the synergistic impact of distinct components.