Wilson disease is an autosomal recessively inherited disease of copper metabolism and is characterized by liver and central nervous system dysfunction. The heterozygote carrier state rate is about one in 90 persons and the incidence of the disease is about 30 in 1,000,000. Although leukemia is the most common form of childhood malignancies, the probability of the presence of Wilson disease and acute lymphoblastic leukemia in the same patient is very low. We report an unusual case of a child with Wilson disease who developed acute lymphoblastic leukemia in three months.