Background and Objective: Due to inclusion of nano titanium dioxide in substances such as sunscreens and detergents which may be used by pregnant mothers and regarding that the studies on the effects of such substances have not yet been clearly elucidated, therefore, we conducted this study to investigate the effect of TiO2 on forelimb buds in mouse embryos. Materials and Methods: In this study, five groups of forelimb buds including control, sham, experimental group 1 (using a dose of 30 mg/kg), experimental group 2 (using a dose of150 mg/kg) and experimental groups 3 (using a dose of 500 mg/kg), were investigated. On day 11 of gestation, control group without the effect of TiO2, sham group with injection of deionized water as TiO2 solvent and experimental groups with injection of TiO2 (10 nm particles) with doses of 30, 150 and 500 mg/kg mouse weight were examined. Then, on day 15 of gestation, embryos were removed from the mothers’ body and their forelimb buds were amputated. Results: The findings revealed a significant increase in doses 30 and 150 mg/kg in the total length of limb bud, skin thickness, the number of mesenchymal cells in fingers, degenerating chondrocyte cells in arm, and a significant decrease in the number of proliferating chondrocyte cells in arm, mesenchymal cells in palm and wrist, mitotic dividing mesenchymal cells in fingers and red blood cells in fingers. Meanwhile, it was found that the dose of 500 mg/kg led to a significant decrease in the total length of limb bud, skin thickness of arm, number of proliferating chondrocytes in arm, red blood cells in fingers and mesenchymal cells in palm and wrist. Conclusion: The findings of this study revealed decreasing and increasing effects of cytotoxicity of TiO2 nanoparticles on the growth of forelimb bud in mouse embryos under in vivo conditions.