In the present article, we report, for the first time, a prenatal diagnosis of a congenital mesoblastic nephroma in combination with a post-partum hyperreninemia with hypertension. A newborn was delivered at 35 weeks gestation who had an intrauterine diagnosis of a renal mass as early as 32 weeks gestational age by ultrasound examination. Tumor nephrectomy was performed on day 11 after delivery when an increase in hypertension was observed in the newborn.