Vascular dementia is a common problem caused by falling of blood supply to cortex of brain due to hyperlipidemia and atherosclerosis. Melatonin, a pineal hormone was proved to be effective as antidementia and antihyperlipidemic agent previously. In the present study we evaluated the effect of melatonin (5mg/kg, 10mg/kg, p.o) on hyperlipidemia induced vascular dementia in rats. To mimic the human condition the rats were induced dementia by feeding atherogenic diet for 20days and single shot of triton x100(100mg/kg, i.p). The experiment with combined model of hyperlipedemia( Both chemical and diet induced) was taken up for the first time and able to establish successfully. Parameters like locomotar activity, radial arm maze test, morris maze and active avoidance test, biochemical estimations of total cholesterol, triglycerides, HDL, LDL, super oxide dismutase, Catalase activity, acetylcholine esterase activity and lipid peroxidation products were estimated. The melatonin (10mg/kg, p.o) significantly (P<0.05) improved hyperlipidemia and impaired cognition induced by combination of triton x and atherogenic diet by significantly reversing the levels of TC, TG, LDL, HDL levels, super oxide dismutase, catalase, AchE activity and lipid peroxidation products to normal levels when compared to induced group. Both doses of melatonin 5mg/kg, 10mg/kg showed protective effect but 10mg/kg has more prominent results when compared to5mg/kg. These results indicate that melatonin treatment successfully reduced vascular dementia via its antioxidant mechanism and inhibition of AchE in brain.