Abstract: Electrochemical reduction of nickel sandwich complex-cations Ni(h~5-C_5eR_5) (h~4-C_4R'_4)~+, where R=H, CH_3; R'=CH_3, C_6H_5 was investigated at a Pt-electrode by means of cyclic voltametry, chronopotentiometry and chronoamperometry in dichloromethane, acetonitrile, tetrahydrofuran and propylenecarbonate (PC). The reduction are reversible and single electron processes for the compounds with R=H, R'=C_6H_5; R=CH_3, R'=C_6H_5 and the products are characteristic of “19-electron” nickel complexes. The complex cations exhibit an irreversible processes with coupled chemical reaction when R=H, R′=CH_3; R=CH_3, R′=CH_3. The stability of the reduction products was investigated further by bulk electrolysis. The reversibility of the electrochemical reduction tend to be reduced in THF.