Dinotefuran (DINO) is a third-generation neonicotinoid insecticide with extensive worldwide application, resulting in continued human exposure. The present study explored the reproductive toxicity of DINO on oestrous cycle stages in rat females and the ameliorative role of rosemary leaf extract (RE). Twenty rat females were exposed to DINO, RE, and their combination at 73.5 and 230 mg/kg for 14 days. The levels of estrogen and progesterone were measured, and the dysregulation of oestrous cycle stages was monitored. The exposure to DINO resulted in an imbalance in estrogen and progesterone levels. Also, the regulation of oestrous cycle stages was disrupted. These effects were mitigated when rats were administered RE. Altogether, these findings provide insights into the reproductive toxicity of DINO on rat females and the ameliorative effects of RE on DINO-induced toxicity.