In this work, we utilize the electrohydrothermal (EHT) approach, as a versatile synthesis approach, for fabricating MnO2-decorated Co3O4 (MnO2/Co3O4) composites for supercapacitor applications. This method leverages the strengths of both electrochemical deposition (ED) and hydrothermal (HT) synthesis, offering precise control and high efficiency. Co3O4 and MnO2 are potential candidates for electrode materials in energy storage systems due to their high theoretical capacity, biocompatibility, abundance in nature, and cost-effectiveness. Bimetallic oxide nanocomposites are highly attractive for supercapacitor applications due to integration of multiple redox-active centers with improved electrical conductivity, resulting in higher specific capacitance, improved rate capability, and superior cycling stability. Using EHT approach, hydrothermal conditions were applied in the first step while cobalt hydroxide layer was deposited on Ni foam substrate (NF). The resulting Co(OH)2/NF electrode was subsequently subjected to heat treatment to form the Co3O4/NF electrode. In the second step, the electrodeposition of MnO₂ was performed in the optimized EHT conditions by applying a constant cathodic potential, yielding the MnO2/Co3O4/NF electrode. Notably, MnO2/Co3O4/NF electrode exhibited an ultrahigh specific capacitance of 1207 F g-1 at a high current density of 6 A g-1, along with a 62% rate capability when the current density was increased from 6 to 25 A g-1. Besides, the electrode materials demonstrated excellent cycling stability and capacitance retention of almost 91% beyond 10,000 successive cycles. Furthermore, an asymmetric capacitor (ASC) was fabricated using MnO2/Co3O4/NF as positive electrode and 6 M of KOH as electrolyte to evaluate its electrochemical performance. The ASC device delivered an impressive energy and power densities of 54.8 Wh kg-1 and 44.14 kW kg-1, respectively. Our findings corroborate the superior capacitive performance of MnO2/Co3O4 electrode materials fabricated by an electrohydrothermal approach.