Castleman disease (CD) is an uncommon lymphoproliferative disorder and is especially rare in the retroperitoneum or perirenal area. We report the case of a 42-year-old woman in whom we found on routine physical examination a mass localized in the right abdomen without clinically important constitutional symptoms for 30 days. Abdominal ultrasound, magnetic resonance images and computed tomography scans revealed a solid mass localized just below the right kidney in the retroperitoneum. The patient subsequently underwent an exploratory laparotomy. Pathological examination revealed a right retroperitoneal mass of CD (hyaline vascular type). The patient completely recovered after surgery. Castleman disease is commonly misdiagnosed as malignant lymphoma, lymphadenitis or ectopic thymoma. So far, its diagnosis is mainly achieved via histopathological examination of surgically obtained tissue. After removal of the lesion, local CD has a good prognosis.