Urachal abnormalities represent a rare pathology and, in case of presence, they are more frequent in children and, among adults, in men. We report a case of urachal cyst in an adult woman in whom it was difficult to determine preoperatively the origin of the abdominal tumor. Positive diagnosis and treatment implied surgical exploration and resection. Even rare, this pathology should be considered in the differential diagnosis of an abdominal cyst. While the diagnosis may be established by clinical examination and imaging methods, surgical exploration is justified and, besides, offers the therapeutic opportunity.