It is extremely rare that a patient with anaplastic large cell lymphoma (ALCL) demonstrates circulating lymphoma cells. A 10-year-old Japanese boy was presented with high-grade fever and cough. The physical examination revealed marked hepatosplenomegaly with ascites and lymphadenopathy in the cervical and periauricular areas. The white cell count was 26.2×109/L with 95% of abnormal lymphoid cells, which were small to medium-sized with a high nucleus/cytoplasm ratio, basophilic cytoplasm, condensed nuclear chromatins, and 1 or 2 distinct nucleoli, hemoglobin 6.4 g/dL, and platelet 0.9×109/L. A flow cytometric analysis of abnormal cells in both the peripheral blood and bone marrow samples was strongly positive for CD30 on their cell membranes. Karyogram and fluorescent in situ hybridization showed abnormal cells to have a characteristic chromosomal translocation, t(2;5)(p23;q35). Reverse transcriptase-polymerase chain reaction of peripheral blood cell-derived mRNA also indicated the fusion gene product of anaplastic lymphoma kinase and nucleophosmin. Subsequently, the patient was diagnosed to have ALCL with a rare clinical feature of a peripheral leukemic presentation, and his disease revealed to be refractory to chemotherapy. On the basis of the 11 childhood cases of ALCL with leukemic presentation so far published and reviewed herein, the prognosis is very poor.