This study was carried out to verify the therapeutic role of Prussian Blue (PB) in removing internal [137Cs] contamination from rats and to evaluate any side effects caused by chronic consumption of this compound on hematological (RBCs, Hb) parameters, serum biochemical contents (total proteins, albumin, globulins, A/G ratio, urea, urea nitrogen, creatinine, cholesterol, calcium, sALT and sAST enzymatic activity, bilirubin) and thyroid function (T4 and T3). PB administration before or at the time of irradiation could eliminate the decreased or increased effects of [137Cs]-gamma irradiation on: RBCs, Hb, total proteins, globulins, creatinine, urea, urea nitrogen, SAT, T3, T4. However, PB administration, one or seven days post irradiation eliminated [137Cs]-gamma irradiation effects on: cholesterol, calcium, bilirubin in both of growing and adult rats.