Surface area, pore properties, synergistic behavior, homogenous dispersion, and interactions between carbon matrix and metal-nanostructures are the key factors for achieving the better performance of carbon-metal based (electro)catalysts. However, the traditional hydro- or solvothermal preparation of (electro)catalysts, particularly, bi- or tri-metallic nanostructures anchored graphene (G) or carbon nanotubes (CNTs), often pose to poor metal–support interaction, low synergism, and patchy dispersion. At first, bimetallic flower-like-CuFeS₂/NG and cube-like-NiFeS₂/NCNTs nanocomposites were prepared by solvothermal method. The resultant bimetallic nanocomposites were employed to derive the 2D-nano-sandwiched Fe₂CuNiS₄/NGCNTs-SW (electro)catalyst by a very simple and green urea-mediated “mix-heat” method. The desired physicochemical properties of Fe₂CuNiS₄/NGCNTs-SW such as multiple active sites, strong metal-support interaction, homogenous dispersion and enhanced surface area were confirmed by various microscopic and spectroscopic techniques. To the best of our knowledge, this is the first urea-mediated “mix-heat” method for preparing 2D-nano-sandwiched carbon-metal-based (electro)catalysts. The Fe₂CuNiS₄/NGCNTs-SW was found to be highly effective for alkaline-mediated oxygen evolution reaction at low onset potential of 284.24 mV, and the stable current density of 10 mA cm⁻² in 1.0 M KOH for 10 h. Further, the Fe₂CuNiS₄/NGCNTs-SW demonstrated excellent catalytic activity in the reduction of 4-nitrophenol with good k_app value of 87.71 × 10⁻² s⁻¹ and excellent reusability over five cycles. Overall, the developed urea-mediated “mix-heat” method is highly efficient for the preparation of metal-nanoarchitectures anchored 2D-nano-sandwiched (electro)catalysts with high synergism, uniform dispersion and excellent metal-support interaction.