The effect of Mn₃O₄ addition on microhardness, microstructure and electrical properties of vanadium oxide doped zinc oxide varistor ceramics is systematically investigated. The Vicker's microhardness H_V has decreased with increasing the amount of Mn₃O₄. Also, the average grain size has decreased from 27.51 μm to 19.55 μm with increasing the amount of Mn₃O₄ up to 0.50 mol%, whereas an increase in Mn₃O₄ up to 0.75 mol% has caused the average grain size to increase and then it decreases with increasing Mn₃O₄ from 0.75 mol% to 1.00 mol%. The sintered density has decreased from 5.38 g/cm³ to 5.31 g/cm³ with increasing the amount of Mn₃O₄. The varistor ceramic modified with 0.50 mol% Mn₃O₄ has exhibited excellent nonlinear properties, with 16.29 for the nonlinear coefficient and 441.9 μA/cm² for the leakage current density. Furthermore, the sample doped with 0.50 mol% Mn₃O₄ has been found to possess donor density as 0.77×10¹⁸ cm^-3 and 0.916 eV barrier height.