For the first time, a new electrocatalytic mechanism of the electrochemical behavior of chlorpromazine has been evaluated. At a boron doped diamond (BDD) working electrode, the electrochemical behavior of aqueous chlorpromazine (CPZ) and chlorpromazine/l-cysteine at 0.3–1.3V were studied by cyclic voltammetry (CV) technique. The results showed that the electrochemical oxidation of chlorpromazine has a mechanism of EEC. As well as, the electrocatalytically properties of CPZ were investigated in the presence of l-cysteine amino acid. The results indicate a complicated catalytic system. Based on the results, this system is involved in the EC'EC mechanism. For both the obtained mechanisms, the effect of increasing concentration and the effect of the rate of potential scanning were studied. the impact of empirical parameters on the shape of the voltammograms is examined based on an EEC and EC'EC mechanisms. The kinetic parameters were calculated by fitting the Digital Simulation3 program to those generated by experimental cyclic voltammograms for EEC and EC'EC mechanisms.