Deltamethrin is a broad spectrum, non- cumulative, fast acting neurotoxic synthetic pyrethroid. The aim of this study was to analyze the neurotoxicity induced by deltamethrin which caused neuro-oxidative stress, histopathological & immunohistochemical changes in adult male Wistar rats and to evaluate the possible ameliorative effect of melatonin. Melatonin (10mg/Kg, once daily), ethanol 99% (1 ml/kg, once daily), corn oil (0.005ml/Kg, once daily), deltamethrin (12.5mg/Kg, once daily), and melatonin (10mg/Kg) + deltamethrin (12.5mg/Kg) combination were given to rats I.P for 8 weeks. By the end of 8^th week, rats given deltamethrin alone had significantly higher MDA (malondialdehyde), lower reduced glutathione and catalase levels in the hippocampus and lower ACTH (adrenocortocotrophic hormone) & cortisol hormone levels than the control group. Co- treatment of deltamethrin with melatonin had an ameliorative effect on the previous parameters. Light microscopic investigations revealed that deltamethrin caused marked degenerative changes in the hippocampus & pituitary gland of rats. Mild degenerative changes were observed in rats received deltamethrin + melatonin combination. Immunohistochemical studies revealed that deltamethrin caused marked expression of P-53 (a marker for apoptosis) in the hippocampus & pituitary gland. Mild expression of P-53 was observed in rats received deltamethrin & melatonin combination. Thus, deltamethrin can induce oxidative damage in rat brain & melatonin has an ameliorative effect against this damage.