The three-dimensional porous ceria (CeO2) nanostructures and cobalt (Co) doped porous ceria with different cobalt contents (1 %, 2.5 %, 5 %, and 10 % wt%) were prepared by using the auto-combustion technique. Several characterization techniques, including ICP elemental analysis, XRD, DR UV-Vis, SEM, and TEM, were utilized to describe the fabricated products. The findings confirmed the incorporation of cobalt ions into the ceria framework. Furthermore, the light absorption property of cobalt-doped porous ceria samples was observed to be red-shifted, with the calculated bandgap decreasing from 3 to 2.1 eV for neat porous ceria and 10 % Co doped ceria, respectively. The photocatalytic efficiency of cobalt-doped porous CeO2 was investigated in the decolourization of methyl green dye by utilizing visible light illumination. The photocatalytic data obtained revealed a remarkable increase in activity that is nearly three times greater than the un-doped ceria sample. Furthermore, the best performed cobalt-doped ceria sample was reusable until the fourth consecutive reaction without treatment.