<p>Mn/Co/SnSe nanoparticles were synthesized using the co-precipitation method with the ratios Mn_xCo_ySn_{(1−x)(1–y)}Se (where x = 0.1–0.5 and y = 0.1–0.5) coded MCSS-1, MCSS-2, MCSS-3, MCSS-4 and MCSS-5 nanoparticles. Mn_xCo_ySn_{(1−x)(1−y)}Se nanoparticles were characterized with X-ray diffraction (XRD), UV-absorbance spectroscopy, and scanning electron microscopy (SEM). The XRD analysis revealed that the Mn_xCo_ySn_{(1−x)(1−y)}Se nanoparticles possess an orthorhombic structure, with average crystallite sizes below 100&#xa0;nm. The SEM images showed that the surface morphology of the Mn_xCo_ySn_{(1−x)(1−y)}Se nanoparticles was not perfectly spherical, displaying small spherical shapes and rod-like structures. The optical properties were examined using UV–Vis spectroscopy, indicating that the highest absorbance occurred between 200 and 400&#xa0;nm. The cyclic voltammograms (CV) graph shows the pseudocapacitance nature of the Mn_xCo_ySn_{(1−x)(1−y)}Se nanoparticles. The MCSS-1 electrode has a coulombic efficiency and capacitive retention of 93% and 94.98% whereas the MCSS-4 electrode has 95% and 96.68%. The increase in the coulombic efficiency and capacitive retention from MCSS-1 to MCSS-4 electrodes show an increasing tendency with the incorporation of dual-doped Mn/Co dopants.</p>