Imidazolium dichromate (IDC) oxidizes benzyl alcohol and substituted benzyl alcohols have been studied in aqueous acetic acid and in the presence of acid to the corresponding aldehydes. The reaction was carried out under pseudo-first order conditions. The reaction has unit dependence on each of the benzyl alcohol and IDC. The reaction is catalyzed by hydrogen ions. The decrease in dielectric constant of the medium increases the rate of the reaction. Electron-withdrawing substituent on benzyl alcohol reduces the rate of oxidation, while electron-donating group enhances the rate compared to the unsubstituted benzyl alcohol. However, correlation of the logarithm of the rate constant with the Hammett’s substituent constant s gives a smooth curve. This is explained due to the operation of substituent effect on two steps of the mechanism proposed.