Electrochemical water splitting has a bright future in creating high-density and green hydrogen, but the sluggish H₂O dissociation process, which is hampered by low H₂O adsorption on the catalyst surface, is a major barrier to large-scale industrial electrochemical water splitting. Defect engineering, interface engineering, facet engineering, and morphology design are just a few of the effective ways for synthesizing highly efficient electrocatalysts with adequate H₂O adsorption. The insertion of foreign elements into the crystal lattice is a straightforward technique to modulate interaction for improved catalytic activity (referred to as doping). The introduction of dopants in the parental host materials has a significant impact on their physicochemical characteristics. The work features a highly stable kinetic for the electrocatalyst MnSe₂@3 wt% that exposed a ɳ₁₀ (overpotential at 10 mA/cm²) of 171 mV (Tafel slope of 147 mV/dec for hydrogen evolution) and MnSe₂, 270 mV (Tafel slope of 160 mV/dec for oxygen evolution). Further, in support of the systematic density functional theory simulations using first-principle calculations were carried out to address the detailed modifications in electronic structures and resulting orbital interactions. Clear enhancement near the Fermi level is caused by the charge transfer from the metal d orbital and Se p orbital to the p orbital of the dopant sulfur. The charge transfer, increased surface area, and improvement in conductivity may be the driving force for improved OER and HER activities for the sulfur-doped materials as observed in the experiment. This work comparatively showcases the metal selenide structures with optimized S-doping in order to ascertain the relevance of S-doping in boosting water splitting electrocatalyst.