The purpose of this study was to evaluate whether polybrominated diphenyl ethers (PBDE) at levels reported for human populations affect the thyroid state in pregnant sheep and lambs. Pregnant sheep were exposed to vehicle or BDE-47 (0.2, 2 and 20 μg/kg b.w.) from the 5th to 15th week of gestation by intravenous injections weekly. Thyroid hormone levels and BDE-47 content in the blood of sheep and lambs and adipose tissue were analyzed. We observed a significant decrease in total T4 and T3 in exposed lambs without any effect in pregnant sheep. Our finding indicates that prenatal low-dose PBDE exposure results in PBDE storage in fat of offspring and can affect thyroid metabolism in the developing fetus.