Nano/mesoporous transition metal oxides have attracted extensive attention because of their distinctive morphology and properties, along with exhibiting better performance in many applications. We employed a simple modified version of the one-pot co-precipitation method at room temperature to synthesize three-dimensional mesoporous microstructures obtained by the self-aggregation of Co3O4 nanoparticles, which is sparse in the literature. The obtained structures were used as electrode materials for electrochemical capacitors or supercapacitors. The as-obtained Co3O4 electrode exhibited acceptable specific capacitances of 400 and 165 Fㆍg-1 at applied current densities of 1 and 10 Aㆍg-1, respectively, with over 99% of capacity retention after 4000 cycles.