Background:  Propylthiouracil, an antithyroid drug used to treat hyperthyroidism in pregnancy. Optimal treatment of hyperthyroidism during pregnancy is essential for favourable pregnancy outcome. Aim: The aim of this study is to observe the teratogenicity of Propylthiouracil given during organogenesis period of gestation on fetal liver. Methods: Pregnant Swiss albino mice were given Propylthiouracil in the dose of 100 mg/kg body weight/day orally on 6, 7 & 8th days of gestation, while control mice were given same volume of distilled water orally for same duration. The pregnant mice were sacrificed on 18th day of gestation and foetuses were collected. The fetal liver were dissected out, formalin fixed and processed for histological study with H&E staining. Result: The treated liver, on gross examination shows reduction in size and weight. While histological examination shows dilatation of central vein and sinusoids with breakage of their lining endothelium and clumping of pyknotic hepatoblasts around central vein along with destruction of liver parenchyma. Conclusion: Propylthiouracil should be used cautiously in pregnancy to avoid risk of congenital malformations due to its hepatotoxic effect.