ABSTRACT This study investigated electrical properties and microstructure of zinc oxide varistors containing MnO2, Cr2O3, V2O5 and TiO2. To this end, nanosize ZnO particles were synthesised by the polyacrylamide-gel method and doped with minor amounts of MnO2 (0.5 mol-%), Cr2O3 (0.5 mol-%), V2O5 (2 mol-%) and TiO2 in the range of 2–15 mol-%. The prepared samples sintered at 1050°C in air for 2 h. It was observed that TiO2 promoted grain growth of ZnO particles. X-ray examination showed hexagonal ZnO structure as a main phase and Zn2TiO4 and ZnV2O4 as minor secondary phases. The nonlinear coefficient and threshold voltage of the prepared samples were in the range of 3.3–7.9 and 1120–4700 V cm−1 respectively, in which both of them increased with increase in TiO2 content. Among the prepared samples, the varistor with 15 mol-% TiO2 exhibited the best performance in terms of nonlinearity. The nonlinear electrical behaviour was explained by theory of formation of the potential barriers at grain boundaries.