Aggressive natural killer cell leukemia (ANKL) is an extremely rare type of leukemia characterized by clonal NK cell infiltration of peripheral blood and the bone marrow, cytopenias, and hepato/splenomegaly. ANKL is an aggressive subtype of a large granular lymphocytic (LGL) leukemia. Peripheral blood smear shows LGL cells containing characteristic azurophilic granules in a light pale basophilic cytoplasm and immature nuclei. Immunological studies determine CD3-/CD16+/CD56+ and cytoplasmic CD3+. Tumor cells may have EBV positive. Chemotherapy resistance is caused by a multi-drug resistance gene (MDR); thus, patients die within 2 months after diagnosis. Here, we report a rare case of a patient diagnosed with ANKL.