Mechanistic and kinetic investigation of oxidation of L-Serine by pyridinium chlorochromate in DMF-water mixture containing perchloric acid has been studied at 40ºC. The rate of reaction was found to be of first order dependence on [PCC], [L-Serine] and [H+]. The increase in the rate of oxidation with increase in acidity indicates the involvement of a protonated chromium(VI) species in the rate-determining step. The product of oxidation has been identified as an aldehyde. The rate of reaction decreased with increase in the polarity of medium, which indicates that there is involvement of an ion-dipole type of interaction in the rate-determining step. On the basis of the experimental findings, a suitable mechanism has been proposed.