It is occasionally difficult to distinguish Wegener's granulomatosis (WG) from other diseases including malignancy, tuberculosis, and various types of vasculitis because of the overlapping symptoms and signs. We report on a patient with NK/T cell lymphoma who was treated with a limited form of WG. At his first visit, he presented with left foot drop and recurrent nasal swelling. Necrosis and massive infiltration of inflammatory cells were identified on a nasal tissue biopsy. Sural nerve biopsy findings also showed infiltration of inflammatory cells in both the endoneurium and perivascular area; thus, a diagnosis of a limited form of WG was made. After combination therapy with a glucocorticoid and oral cyclophosphamide was initiated, his condition completely recovered without recurrence for the next 2 years. However, he visited the hospital again for recurrence of nasal swelling. Repeated biopsy of nasal tissues, combined with an immunophenotypic analysis revealed NK/T cell lymphoma. The possibility of NK/T lymphoma should be considered when evaluating a limited type of WG, which shows atypical findings on biopsy as well as recurrent deterioration, as a suboptimal dose of immunosuppressive therapy may mask its expression and lead to a poor prognosis.