The central nervous system is the most important system and is very sensitive to any accidental infection during ontogenesis; it includes brain and spinal cord. The cerebellum is the second largest part of the brain after cerebrum and it’s very sensitive to the abnormal changes during the embryological development. This study was designed to investigate the effect of the maternal exposure of selected concentrations of suspension of nanoparticles on the ontogenesis of the rat cerebellum after embryos implanted in uterus. A total of 60 female pregnant rats were divided in to three groups, each contains 20 females. Group1 (G1) was treated orally with 2mg/kg /body weight (b. wt) of suspension of silver nanoparticles (Ag NPs). While group 2 (G2) was treated with 20mg/kg/b. wt of AgNPs after implantation from 7th day of pregnancy until delivery at day 21st, for 15 day. And group3 (G3) was considered as control whose received Distal water (D.W) only. We had selected the following embryonic day for treatment (ED12, 15, 18 and 21). The histological results showed a defect in the ontogenesis of the cerebellum cortex layers of embryos, through lack of density of external granular layer, as well as degeneration and dispersion of the glial cells in the internal granular layer of cerebellar cortex, in addition to less distribution of cells in the molecular layer due to the ability of AgNPs to pas the placenta and blood brain barrier (BBB) to the embryo’s brain after female exposure to the AgNPs during pregnancy. AgNPs at low concentration 2mg/kg/day and higher concentration 20mg/kg/day can produce many histological toxicity to the embryo’s hindbrain and cerebellum when administrated to the dams during pregnancy period.