<p>Although ferrite-based materials offer good theoretical capacitance and stability, their poor electrical conductivity limits practical supercapacitor performance. Previous studies have explored carbon-based composites to address this issue; however, optimized integration and systematic investigations of cobalt-doped magnesium ferrite combined with multi-walled carbon nanotubes (MWCNTs) are still limited. The purpose of this work is to overcome these limitations by incorporating varying amounts of multi-walled carbon nanotubes (MWCNTs) into cobalt-doped magnesium ferrite (Mg₀.₉₁Co₀.₀₉Fe₂O₄) to develop advanced nanocomposites for energy storage. In this work, we synthesized cobalt-doped magnesium ferrite nanoparticles (Mg₀.₉₁Co₀.₀₉Fe₂O₄) combined with varying amounts (0–15 wt%) of multi-walled carbon nanotubes (MWCNTs) to form nanocomposites using an ultrasonication-assisted method at room temperature. The structural analysis showed a progressive reduction in crystallite size from 20.57&#xa0;nm (0 wt% MWCNT) to 16.17&#xa0;nm (15 wt% MWCNT), while surface area increased from 62.82 to 81.76&#xa0;cm²/g, accompanied by a rise in porosity from 10.26% to 24.39%. Electrochemical characterization was performed using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). At a current density of 1 Ag^− 1, the specific capacitance increased significantly from 438 Fg^− 1 for the pure ferrite sample to 1603 Fg^− 1 for the 15 wt% MWCNT nanocomposites. Corresponding energy and power densities also improved, from 11 Whkg^− 1 and 216 Wkg^− 1 (0 wt%) to 46 Whkg^− 1 and 228 Wkg^− 1 (15 wt%). These enhancements are attributed to the increased surface area, improved conductivity, and synergistic interaction between MWCNTs and the ferrite matrix. The results suggest that the optimized nanocomposite holds strong promise for high-performance supercapacitor applications.</p>