Engineering active interfaces in 2D materials is vital for advancing supercapacitors. Here, Mo-doped ReS2 was synthesized via a single-step hydrothermal method, enhancing electrochemical properties. Mo doping introduces unsaturated electrons and defect-rich sites, improving conductivity and charge transport in ReS2. Structural and compositional analyses (SEM, TEM–EDX, XRD, Raman, XPS) confirm successful Mo incorporation. Electrochemical testing in a three-electrode setup using 1 M Na2SO4 (1 mg cm−2 loading) showed that 10% Mo-ReS2 delivered a specific capacitance of 163.7 F g−1 at 0.5 A g−1, a 61% improvement over pure ReS2. It also achieved 22.6 Wh kg−1 energy density, 250 W kg−1 power density, and 206.3 F g−1 at 5 mV s−1 from CV. Notably, it retained 91.75% of its capacitance after 5000 GCD cycles, demonstrating excellent stability. These results underscore the synergistic role of Mo doping and interface engineering, positioning Mo-ReS2 as a promising material for energy storage applications.