The authors report the first case of prenatal fetal MRI diagnosis of unilateral hydrocolpos, uterus didelphys, and ipsilateral renal agenesis in a case of obstructed hemivagina and ipsilateral renal anomaly (OHVIRA) syndrome. A 33-year-old woman was referred to the present institution because of a fetal pelvic cyst. Detailed ultrasound revealed a female fetus with a retrovesical cyst and right renal agenesis. Fetal MRI confirmed unilateral hydrocolpos, uterus didelphys, and normal intestinal tract of the fetus. Fetal MRI is a useful modality for prenatal diagnosis of OHVIRA as a method of evaluating the pelvic structures and excluding other cloacal anomalies.