Fast Green FCF (FGF) is a synthetic food dye. The kinetics of oxidation of Fast Green FCF with 1-chlorobenzotriazole in NaOH medium has been spectrophotometrically investigated at ƛmax 625 nm at the temperature 301 K. The reaction exhibited a pseudo -first order dependence of the rate on [FGF], first order dependence on the rate of [CBT]0, fractional order dependence on [OH-]. And inverse fractional order on addition of reduced product [BTA]. It fails to induce polymerization of acrylonitrile under the experimental conditions employed. Thermodynamic parameters for the reaction have been evaluated. Effects of dielectric constant and ionic strength of the medium on the reaction rate have also been studied. Oxidation products are identified and characterized by LC-MS. A probable reaction scheme is proposed and an appropriate rate law is deduced to account for the observed kinetic data.