In this paper, we have studied the electrochemical behavior of indigo carmine (IC) in the presence and absence of mediator molecules. We have used three azo dyes as mediators in our studies and the effect of mediator molecules on the electron transfer between the IC solution and the electrode surface was explained from the cyclic voltammograms data. Among these dyes, 4-(4-nitrophenilazo)N-benzyl,N-ethylaniline (NBE) showed good performance as an electron transfer mediator. The NBE/carbon paste was characterized with Fourier transform infrared spectroscopy and scanning electron microscopy methods. The redox peak currents of IC were enhanced significantly compared with those obtained at the unmodified electrode. Some parameters affecting sensor response were optimized and then the calibration curve was plotted. The oxidation peak current was proportional to the concentration of IC from 1 to 100μmolL–1. The detection limit was 0.36μmolL–1. The proposed electrode was successfully applied to the determination of IC in various real samples without complex sample pretreatment. Display omitted •The electrochemical behavior of IC in the presence and absence of mediator molecules was studied.•The results showed that NBE molecules were an effective mediator for the electron transfer.•The redox peak currents of IC were enhanced significantly compared with that obtained at the unmodified electrode.•The proposed electrode was applied to the determination of IC in various real samples without complex sample pretreatment.