Recently, hybrid supercapacitors have attracted tremendous attention as promising energy storage and conversion devices due to their excellent energy density and high power density. In the present work, a novel pioneering hybrid ternary nanocomposite of NiO/Gr/PPy was synthesized by a low-cost co-precipitation method, followed by heat treatment and in-situ chemical polymerization. The as-synthesized nanocomposite was drop-cast on a modified Cu current collector to enhance the supercapacitive performance and stability in the electrolyte. The results of electrochemical characterization in 6 M KOH revealed the high specific capacitance and energy density of 970.85 F g−1 and 33.71 Wh kg−1 at 1 A g−1, respectively. This can be attributed to the synergic effect and hybrid performance of NiO, Gr, and PPy. Moreover, a full symmetric cell was assembled by using this hybrid ternary nanocomposite and evaluated in TEA-BF4/AN. The results showed the high specific capacitance and energy density of 66.17 F g−1 and 36.76 Wh kg−1 within the 2 V potential window, respectively.