Renal vein thrombosis (RVT) occurs as an acute and life-threatening event in neonates. RVT is the most common non-catheter-related thrombosis in infancy and occurs primarily in the newborn period. Non-catheter-related abdominal thrombosis on neonates has a higher incidence of genetic prothrombotic risk factors. RVT and adrenal hemorrhage can both be encountered in the neonatal period and they may occur at the same time (Bokenkamp et al., Eur J Pediatr 159:44-8, 2000; Lau et al. Pediatrics 120:1278-84, 2007). We report a case of unilateral RVT and adrenal hemorrhage in a newborn with homozygous factor V Leiden mutation and heterozygous of the methylene tetrahydrofolate reductase (MTHFR) gene mutations.