The burst of energy produced from the sustainable energy sources need to be harnessed by energy storage systems. Development of novel and advanced energy storage devices such as supercapacitors discover an enormous future ahead. Recently, hybrid supercapacitors (electric double layer capacitor (EDLC) and pseudocapacitors) trend to be used as energy storage interfaces for their improved efficacy in energy density without altering the power density. In the ongoing workplan, transition metal selenides MnSe₂ and its hybrid with multiwalled carbon nanotubes (MWCNTs) are synthesized by a simplistic hydrothermal protocol. Certainly, cubic phases of MnSe₂-MWCNT(MS/CNT) manifested superior electrochemical performance in both symmetric and asymmetric full cell configurations in contrast to prestine MnSe₂(MS). The asymmetric MS/CNT cell achieved an excellent charge storage capability with an high energy density of 39.45 Wh kg⁻¹ at a power density of 2.25 kW kg⁻¹ maintaining an energy density of 14.5 Wh kg⁻¹ at a high power density of 4.5 kWh kg⁻¹ and also revealed long term stability over 5000 consecutive charge/discharge cycles (capacitance retention of 95.2%). Furthermore, the preferable growth along (2 0 0) direction in the presence of MWCNTs favoured in enriching the supercapacitive property of MS. The quantum capacitance of MnSe₂ surfaces and MS/CNT heterostructure has been estimated using density functional theory simulation to confirm the experimental outcomes. Theoretical investigation simultaneously exposed the contribution of (2 0 0) plane of MnSe₂ and MWCNTs cultured in enhanced DOS (density of states) near the Fermi level that remarkably promoted the energy storage efficiency of MS/CNT.