Bi(III) ions electroreduction in the presence of N-acetylcysteine (ACYS)at the nanostructured R-AgLAFE electrode has been studied by the voltammetric and impedance measurements. The experimental data indicates the multistage character of the electrode process and the catalytic influence of N-acetylcysteine on the Bi(III) ions electroreduction rate. It was found that this process is controlled by the chemical reaction of the Bi(III)–Hg(SR)2 activecomplexes formation on the electrode surface, which mediates electron transfer. Active complexes are a substrate in the process of electroreduction, and their different structure and properties are the reason for the diverse catalytic activity of N-acetylcysteine.