Abstract: The aim of this study was to investigate ultrastructural changes of Cerebellum in 3mT electromagnetic field exposed rats. Total 30 adult female Wister rats with 3 months of age and weighing 210±10.6 g were used in this study. All female rats subdivided randomly to 2 groups: group 1, serve as untreated controls; group 2, was exposed to 3mT EMF for 4 months, 4 h day-1. After 120 days all rats were killed and their tissue samples from Cerebellum were removed and prepared for electron microscopic studies. Present finding clearly demonstrated that number of purkinje cells in the cerebellum of EMF- exposed rats were decreased significantly (p<0.01) in comparison to control group. The other changes include: condensation of nuclei, dilatation of endoplasmic reticulum, breakdown and disappearance of crista in mitochondria and vacuolization of cytoplasm in the purkinje cells of cerebellum. The mean nuclear diameter in purkinje cells were 45.35±22.85 mm and 26.79±16.36 mm in control and experimental group respectively. The statistical analysis showed that the difference between two group was significant (p = 0.03). Axial ratio of nucleus of purkinje in control and experimental groups were 1.86±0.41 and 1.55±0.14 mm, respectively. The axial ratio of nucleus in purkinje of EMF-exposed cerebellum were decreased significantly in comparison to control group (p = 0.02). These findings indicate that long-term exposure to EMF has detrimental effects on central nervous system at cellular level.