Background: Hexaflumuron (HFM) is an insect growth regulator (IGR); it is highly effective against a wide range of pests. Aim of the work: Due to the lack of toxicological assessments of this insecticide especially the formulation type, the objective of the present study was aimed to investigate the toxicological effects of repeated exposure of HFM formulation on adult albino rats. Materials and methods: Three groups were administered daily by gavage for (28 days) at dose of 11, 4, and 2.5 mg/kg b.wt respectively. In addition to control group. Results: The results of acute toxicity indicated HFM exhibited moderate to some extent high toxicity toward the treated rats. Slight tremors and bleeding from nose were observed. The repeated exposure results revealed the high and middle doses exhibited methemoglobinemia. Also, the HFM treatment led to increase in AST and ALT levels. The urea and creatinine levels were not significantly increased except the level of creatinine in high dose. According to the histopathological findings the middle and low doses of HFM revealed greater injurious in liver and spleen tissues than induced by high dose. HFM induced a statistically significant increase in the micronucleus (MN) frequency in a dose-dependent manner compared with a negative control group. Conclusion: So, it is obvious the middle and low doses induced damage in the liver and spleen organs while the high dose induced damage in blood, bone marrow, and kidney organs.