A 23-year-old man without a history of tuberculosis presented with right lower abdominal pain and a fever. An increased inflammatory response was found, and abdominal computed tomography showed a diffuse enlargement and wall thickening in the appendix. An ileocecal abscess and perforating appendicitis were suspected. Therefore, an emergency operation was performed. The surgery revealed a diffuse enlargement with adhesion to the retroperitoneum, which was suspected to be a neoplastic lesion of the appendix, thus an ileocecal resection including the appendix was performed. A histopathological examination revealed a number of epithelioid granulomas having Langerhans giant cells with caseous necrosis in the appendix, in addition to many granulomas without caseous necrosis in the regional lymph nodes. No tubercle bacilli were detected by Ziehl-Neelsen staining. Further examination revealed no tubercular lesions in other organs, thus leading to the diagnosis of primary tuberculosis of the appendix. This is an extremely rare disease reported in Japan.