Water splitting and CO2 conversion are emerging energy transfer techniques to generate hydrogen and low carbon fuel as eco-friendly energy sources. Herein, a frugal and facile approach is reported for decorating MoS2 nanosheets on copper nanorods to design MoS2/Cu architecture as a trifunctional catalyst for electrochemical water splitting and photocatalytic CO2 conversion. Under optimized conditions, MoS2/Cu electrocatalyst shows high performance at an overpotential of 252 mV for oxygen evolution reaction and 160 mV for hydrogen evolution reaction to attain 20 mAcm−2 and 10 mAcm−2 current densities in alkaline medium. The improved efficiency is mainly credited to the synergistic effect of MoS2 nanosheets and Cu nanorods architecture. The electrode delivered a cell voltage of ~1.508 V to impart about 10 mAcm−2 current density with high durability. Also, the negligible overpotential decay after running the cell for 12 h with 3000/HER and 2000/OER CV cycles suggests remarkable stability that makes it a promising electrocatalyst for energy production. The photocatalytic CO2 conversion activity was also measured, where MoS2/Cu exhibited a significant efficiency of CO2 to methane conversion (CH4 ~ 23 µmol g−1 h−1). Based on the obtained results, it is foreseeable that this work validates the significance of transition metals tuning for electrocatalysts and photocatalysts toward more efficient water electrolysis and CO2 reduction for potential large-scale energy applications.