Corticosteroids and cyclophosphamide are the mainstay of the treatment of microscopic polyangiitis involving pulmonary hemorrhage or rapidly progressive glomerulonephritis. However, patients with advanced age are unable to tolerate this combined therapy, because of a relatively high incidence of side effects including infection, hemorrhagic cystitis, and bone marrow suppression. The authors encountered an 80-year-old patient with pulmonary hemorrhage and renal dysfunction ascribed to microscopic polyangiitis and achieved successful treatment by employing gabexate mesilate in addition to corticosteroids. The present case suggests that gabexate mesilate may be a therapeutic option for microscopic polyangiitis with progressive renal failure and pulmonary hemorrhage.