The aim of this study was to evaluate the potential cytotoxic effects of Benodanil fungicide by employing both mitotic index (MI) and mitotic phases on the root meristem cells of Allium cepa and genotoxic effects by using in vitro micronucleus assay (MN) in human peripheral blood lymphocyte. In the Allium root growth inhibition test, the EC50 value was first determined as 25ppm. Then, 2xEC(50) value (50ppm), EC50 value (25ppm), and 1/2xEC(50) value (12.5ppm) were tested with different treatment periods (24, 48, and 72h). Both negative and positive controls were also used in parallel experiments. We obtained that mitotic index and prophase index decreased when compared with the control in all concentrations. In the micronucleus assay, lymphocytes were treated with various concentrations (250, 500, 750, and 1000 mu g/ml) of Benodanil for 24 and 48h. The results showed that Benodanil did not induce MN frequency in all concentrations of both treatment periods. Additionally, it was determined that this pesticide decreased nuclear division index (NDI) significantly. It was concluded that Benodanil has a cytotoxic effects depending on decreasing of MI and NDI.