Hierarchical nanostructures have recently attracted massive attention due to their remarkable performances in energy conversion, storage systems, catalysis, and electronic devices. Considering the advantage of hierarchical nanostructures, we have formulated a facile and cost-effective chemical bath deposition method to synthesize novel NiCo₂S₄ on a conductive substrate for quantum dot sensitized solar cells & methanol electro-oxidation. Owing to the unique nanoarchitecture, the NiCo₂S₄ electrodes were used to grow high quality thin films containing nanoflowers, nanoplatelets, or nanosheets. The nanoplate-structured NiCo₂S₄ CE in QDSSCs under one-sun illumination (AM 1.5, 100 mW cm⁻²) yielded a high short circuit current density (J_sc) of 11.91 mA cm⁻², open circuit voltage (V_oc) of 0.602 V, fill factor (FF) of 0.50, and power conversion efficiency (η) of 3.53%. These values are much higher than those of the Pt CE (J_sc = 6.98 mA cm⁻², V_oc = 0.579, FF = 0.36, and η = 1.10%). The electrocatalytic performance was investigated by cyclic voltammetry and chronoamperometry for NiCo₂S₄ electrodes via methanol electro-oxidation. Electrochemical studies reveal that the as-prepared NiCo₂S₄–NCS6h electrode displayed a significant enhancement in the electrocatalytic activity and stability for methanol oxidation in the presence of 2 M KOH with 0.5 M methanol. The results indicate that the hierarchical structure of NiCo₂S₄ offers a promising electrode material for QDSSCs and methanol electro-oxidation.