Kikuchi disease (histiocytic necrotizing lymphadenitis) is a rare disorder affecting young women where the presentation is usually with the fever and the self-limiting localized lymphadenopathy. The lymphadenopathy is usually observed in the cervical region, and the involvement of intra-abdominal lymph nodes is quite rare. A 8-year-old boy had been operated under the impression of acute appendicitis at a local clinic due to the acute right lower abdominal pain and tenderness. He was found with a large cecal mass and an intact appendix, and was transferred. Abdominal CT showed the conglomerates of lymph nodes located in the mesenteric area. Mesenteric lymph node excisional biopsies and incidental appendectomy were performed. The biopsy specimen showed many necrotic areas with infiltration of the foamy histiocytes. Laboratory tests revealed increased serum CRP concentration with leukopenia. Serologic tests for viral causes were negative. The postoperative course was accompanied with fever which resolved gradually without a specific treatment. In cases of unclear acute abdomen with a mesentereic lymphadenopathy, an attempt at achieving histological view of a lymph node is desirable in order to realize a rare differential diagnosis such as Kikuchi disease.