We report the structural and nonlinear behavior of Sn 1− x− y Zn x M y O z varistors with x= 0.00, 0.50, y= 0.00, 0.25 and M= Fe, Co, Ni and Mn. The crystallite and grain sizes and porosity of SnO 2 are decreased by Zn doping, followed by a further decrease by (Zn+ M) co-substitution. The breakdown field (E B), nonlinear coefficient (α), leakage current (I K) and residual voltage (K r) of SnO 2 are respectively 333.35 V/cm, 5.6, 900 μA/cm 2 and 5.32. When SnO 2 was substituted by Zn, I K and K r are decreased to 816 μA/cm 2 and 3.62, whereas E B and α are increased to 666.67 and 11.48. The E B and α values are increased by co-substitution in the SnZnMn sample, whereas I K and K r are decreased. Rather than containing many elements and compounds, the current varistors are based on only two well-known ions co-substituted into SnO 2. These findings are discussed in terms of the oxygen vacancies.