The canal of Nuck is the portion of the processus vaginalis within the inguinal canal in women. A hydrocele of the canal of Nuck is equivalent to an encysted hydrocele of the cord in men. The literature reveals very little about this rare condition in the adult female patient. In this paper, we report a case of hydrocele of the canal of Nuck in a young female. The diagnosis was made with ultrasound and magnetic resonance imaging and then confirmed preoperatively and by histopathology. Although rare, a hydrocele of the canal of Nuck has to be included in the differential diagnosis of a groin lump in female patients.