The kinetics of oxidative decarboxylation of N-phenyl glycine (NPG) by peroxomonosulfate (PMS) in perchloric acid medium was investigated at 278 K. The mechanism of the catalytic effect of vanadium(IV) (VO2+) and copper(II) (Cu2+) in the oxidation was also discussed. The oxidation reaction was first-order, with respect to [NPG] in all of the cases. The rate of the reaction decreased with increase in [H+], i.e., the oxidation reaction was acid inhibited. The products were identified by gas chromatography and confirmed by comparing with the authentic sample. The reaction constants involved in the different steps of the reactions were calculated. The catalytic constant (K-c) was determined for the catalyzed reactions and observed that the catalytic efficiency was in the order of VO2+ > Cu2+.