The aerobic oxidation of p-toluic acid to terephthalic acid over tetra(p-chlorophenylporphinato)manganese (T(p-Cl)PPMnCl)/cobalt acetate was reported for the first time. The co-catalysis of T(p-Cl)PPMnCl/Co(OAc) 2 was also studied. The studies indicated that the PTA oxidation was influenced by the catalyst composition, catalyst concentrations and reaction conditions. A preliminary mechanism of this co-catalyzed oxidation reaction was proposed based on experimental observations.