Background: A rare lymph node hyperplasia that resembles malignant tumors is unicentric Castleman's disease. Although, it may appear in any lymph-node basin, the pelvis is an uncommon site for this disease, leading to a challenging preoperative diagnosis. Case Report: A pelvic tumor was discovered during the infertility sort out of a 31-year-old female. Computed tomography scans showed a pelvic mass with prominent vascular-supply, centrally calcified compressing the urinary bladder. With a malignant pelvic neoplasm diagnosis, a laparotomy was scheduled. At surgery, an 11-cm tumor infiltrating right mayor rectus-abdominis muscle, ipsilateral fallopian tube, and a urinary bladder segment was resected en-bloc. The final histopathology diagnosis was a hyaline-vascular, unicentric Castleman´s disease. After seven years of follow-up, the patient is disease-free. Conclusion: Unicentric pelvic Castleman's disease resembles malignant tumors and surgery is mandatory for its treatment and diagnosis.