We report an 81-year-old man who had leukemic presentation of ALK-positive anaplastic large cell lymphoma (ALCL) as an initial manifestation. He had been well after chemotherapy and irradiation for the advanced lung adenocarcinoma, but suddenly suffered from severe lactic acidosis and hypotension. The peripheral blood smear and bone marrow aspiration revealed the infiltration of atypical large cells with horseshoe-shaped or lobulated nuclei. The detection of CD30 expression and the t (2;5) (p23;q35) translocation in these cells was confirmatory of a diagnosis of common variant ALK-positive ALCL in a leukemic phase. He deteriorated rapidly and died before administration of the chemotherapy. An adequate, prompt diagnosis is necessary for this rare disease status in oncologic emergency to improve the disease management.