To our knowledge, this is the first case reported in the literature of umbilical endometriosis in a pregnant woman. We report a case of umbilical endometriosis in a pregnant woman at 16 weeks of gestation. The patient revealed a reddish-brown polypoid nodule within the umbilical depression, with the typical history of monthly bleeding from the umbilicus. A nodule biopsy, testing of serum levels of CA-125 and a transabdominal ultrasound examination were performed. The diagnosis of endometriosis was confirmed by pathological examination. Serum levels of CA-125 were slightly increased and the pelvic ultrasound examination did not identify ovarian cysts of a possible endometriotic nature. The patient was also examined at 24 weeks' gestation, after delivery and in the late postpartum period. No therapy was given and the lesion resolved spontaneously 2 months after the biopsy was taken.