In the present study, the effect of oral administration of imidacloprid over 4 weeks on histological and ultrastructural alterations in brain was assessed in rats. Forty eight male rats were divided into four groups of 12 animals each. Group 1 is control, group 2 was administered with imidacloprid at the rate of 80 mg/kg b.wt/day, group 3 was fed with vitamin C at the rate of 10 mg/kg b.wt/day and group 4 was treated with both imidacloprid and vitamin C for 4 weeks. In group 2, brain section revealed marked congestion in cerebellum, degeneration of purkinje cells with loss of dendrites, vacuolation around neurons and shrunken neurons, vacuolation around neuronal cell body and chromatolysis. The sections of group 4 revealed mild congestion and degeneration of purkinje cells on whereas group 3 animals did not reveal any significant pathological changes. Ultra thin sections of brain revealed vacuolar mitochondria, apoptotic nuclei with disrupted and margination of chromatin material. Group 4 brain section revealed degeneration of neurons. In conclusion, these results suggest that exposure to imidacloprid (80 mg/kg) in male rats induced histological and ultrastructural alterations brain, and coadministration of vitamin C brought moderate protection.