<p>A potentially genotoxic insecticide that is widely used in agriculture is dimethoate-30. This study focused on assessing the cyto-genotoxic impact of dimethoate-30 applying the <i>Allium cepa</i> bioassay, to understand its impact on biota. Roots were treated with 20, 40, 60, 80, and 100 mgl⁻¹ dimethoate-30 concentrations for 24, 48, and 96&#xa0;h, and root growth was measured using mitotic indices. The result showed a significant dose-dependent retardation in mitotic index over to control value, indicating cytotoxicity. Various cytological abnormalities were also observed, including c-metaphase, anaphase bridges, chromosome fragmentation, sticky metaphase and anaphase, and laggard chromosome. In addition, the frequency of micronuclei, aberrant cells percentage, and relative abnormality rate was increased, indicating genotoxicity. These findings indicate that dimethoate-30 may have cytotoxic and genotoxic effects, suggesting that it could be harmful and potentially carcinogenic. Therefore, it is not recommended to use higher concentrations of dimethoate-30 due to its cytogenotoxicity and potential to kill plants.</p>