The catalytic and photocatalytic transformation of S-4(2-), S-3(2-), S-2(2-) and S2- to SO42- by water-soluble cobalt tetrakis (N-methyl-4-pyridyl) porphyrin (Co(4-TMPyP)) was performed by a two-step process. The catalytic autoxidation of S-x(2-) (x = 2, 3 and 4) to S2O32- by Co(4-TMPyP) in the presence of oxygen was followed by the photocatalytic oxidation of S2O32- by Co(4-TMPyP) under illumination in presence of oxygen at a strong basic solution. The direct transformation of S-x(2-) to SO42- was also performed. The catalytic activity of Co(4-TMPyP) was compared to Fe(2-TMPyP) and Mn(4-TMPyP). All three catalysts have activity towards autoxidation of S42- to S2O32-. The trend in photocatalytic oxidation activity of the porphyrin complexes is Co(4-TMPyP) > Fe(2-TMPyP) > Mn(4-TMPyP). The electrocatalytic reactions of S-x(2-) by Co(4-TMPyP) were also observed.