This work studied the effect of self-doped polyaniline (SPANI)-assembled carbon nanoparticles (CNPs) on a supercapacitor. SPANI was in situ polymerised and assembled on CBs by mixing the monomers o-amino-benzenesulphonic acid (SAN) and aniline (AN) with an initiator and CNPs. SAN acted as a self-doped monomer and a surfactant. SPANI-modified CNPs used as an electrode material would improve the performance of CB-based supercapacitor. Variation of the molar ratio of AN/SAN altered the performance of the SPANI-CNP-based supercapacitor. Cyclic voltammetry, galvanostatic charge discharge, and electrochemical impedance spectroscopy were employed to investigate the properties of the supercapacitors. The SPANI CNP-based supercapacitor attained optimal performance at an AN/SAN ratio of 1.0, exhibiting a specific capacitance of 342 Fg(-1) at a charging current density of 0.5 Ag-1 in a symmetric cell.