We report an 11-year-old child with essential thrombocythemia ET, a very rare myeloproliferative disorder among children. Essential thrombocythemia can be complicated by life-threatening thrombosis with a risk of converting into acute leukemia. Cytoreductive therapy may reduce the risk of thromboembolic complications. We usually recommend cytoreductive treatment for asymptomatic adult patients with platelet counts of more than 1.5 million/micro liter, but treatment remains obscure in children. Herein, we report the results of child with ET, treated successfully with hydroxuea.