The aim of this study was to evaluate the characteristic features of patients with mesothelial cyst of the round ligament of the uterus and the incidence of this entity. This was a retrospective review of 3065 patients who underwent inguinal exploration for groin mass from 1998 to 2013. Clinical, radiologic, and histopathologic features of patients with a diagnosis of mesothelial cyst of the round ligament were analyzed. Of the 405 female patients reviewed, 9 mesothelial cysts of the round ligament were identified (2.2%). The median age was 37 (range, 19-82 years). In all patients the groin mass was manually irreducible on physical examination. The lesions were on the right side in 6 (66.6%) patients. These were identified before surgery in 4 (all by groin ultrasonography). Three were misidentified as a hernia before surgery. The remaining 2 (22%) had both hernia and the mesothelial cyst of the round ligament. The cysts were identified after surgery at the time of histopathologic examination in these 2 patients. In all patients histopathologic examination revealed multilobular cystic lesion lined by a single layer of mesothelial cells. Cystic lesions arising from the round ligament were identified and excised along with the round ligament in 7 patients. In the remaining 2, a hernia repair was also performed. There was no recurrence at follow-up. Mesothelial cysts of the round ligament are rare. They are easily misidentified as groin hernia. An accurate diagnosis requires a high index of suspicion and is greatly aided by preoperative imaging studies.