We report a case of a 61-year-old woman with large granular lymphocytosis associated with pulmonary tuberculosis. She was admitted to our hospital because of high fever, anemia and splenomegaly. On admission, the leukocyte count was 6,890/microliters with 52% of large granular lymphocytes. Immunophenotypical analysis of the increased cells showed following results; CD2+, CD3-, CD16+, CD57+. These cells had natural killer (NK) activity. Molecular genetical analysis showed these cells had germline configuration of the T cell receptor beta chain genes. About four months after admission, chest X-P revealed multiple mass shadow and the diagnosis of pulmonary tuberculosis was made by the examination of gastric juice. Anti-tuberculosis therapy was started, and soon after clinical symptom and pancytopenia were improved. For about one year, anti-tuberculosis therapy was continued, and now hematological abnormality is not found. We considered that this case was reactive large granular lymphocytosis of NK cells to lung tuberculosis.