The authors describe a child with an unusual presentation of mesenteric inflammatory pseudotumor in association with leukemoid reaction. An 11-year-old-boy admitted with short stature was found to have an abdominal mass localized in the right lower quadrant. The leukocyte count was 92,000/mm3 with neutrophilic leukemoid reaction. Abdominal ultrasonography and computed tomography revealed a massive calcified mass in the pelvis. Total resection of the mass was performed and the pathologic diagnosis of inflammatory pseudotumor of the mesentery was made. Leukemoid reaction dramatically resolved within a few days after surgical resection. Physicians should be aware of the association of inflammatory pseudotumor, leukemoid reaction, and massive calcification.