 The present study demonstrates a facile, one-step pyrolysis method to synthesize porous carbon nanoparticles using widely distributed Mimosa pudica (Touch-me-not) biomass leaves at different temperatures. Multiple characterization techniques (N2 adsorption–desorption experiments, FESEM, XRD, Raman spectroscopy, XPS) demonstrate the morphological nature and excellent surface properties, with the surface area up to 440.7 m2 g−1. The electrochemical studies of as-synthesized porous carbon nanoparticles, as electrodes, were carried out in both three and two electrode setups. The maximum specific capacitance obtained was 356.1 F g−1 at 0.1 A g−1 in 4.0 M KOH electrolyte. The symmetric supercapacitor showed a specific capacitance of 126.8 F g−1 at 0.1 A g−1 and a high energy density of 34.5 Wh kg−1. The device also showed impeccable stability for 10,000 galvanostatic charge–discharge cycles with 99.2% Coulombic efficiency and capacitance retention of 81.39%. The stability of the device was investigated by floating method (aging), which showed 86.8% capacitance retention, suggesting a huge capacity of biomass-derived carbon materials for efficient and stable high-performance electrodes in electrochemical energy storage applications using an environmental-friendly approach. This study illustrates a sustainable approach to produce porous carbon nanoparticles for effective energy storage devices.