Co₃O₄ as a multifunctional nanomaterial, possessing simultaneously, unique optical, magnetic, and catalytic properties is sparse in the existing literature. We have activated intrinsic multicolor fluorescence covering the entire visible region by the functionalization of Co₃O₄ nanocubes (NCs) with Na-tartrate. The functionalized Co₃O₄ NCs show excellent catalytic efficiency in the degradation of both biologically and environmentally harmful dyes, which opens up a way for the possible application of the NCs toward therapeutic and wastewater treatment. Systematic investigations using UV-visible absorption, steady state, and time-resolved photoluminescence studies reveal the mechanistic origin behind the generation of multicolor fluorescence from the ligand-functionalized Co₃O₄ NCs. Moreover, from the magnetic study we have found that the room temperature antiferromagnetic nature of Co₃O₄ NCs turns to ferromagnetic after ligand functionalization due to the surface modification of the NCs. We believe that the developed multifunctional Co₃O₄ NCs could open up a new horizon toward their diverse applications in the present era of multitasking.