A series of non-oxo vanadium(IV) chelates with tridentate diacidic ligands was studied by cyclovoltammetry using a platinum electrode and by differential pulse polarography using a hanging mercury drop electrode. The reversibility of the electrode processes was observed for the electrochemical redox reaction. A diffusion-controlled one-electron transfer was mostly found. The influence of structural parameters on the stability of the compounds was discussed considering the shift of the reduction potential of the complexes.