Background Chronic congestive hepatopathy is known to cause hepatic fibrosis and portal hypertension in patients post-Fontan operation for single ventricle palliation. The clinical significance of these findings is not clear. We hypothesized that features of portal hypertension would be significantly related to major adverse events. Methods A retrospective review of 73 adult and pediatric post-Fontan patients referred for a liver evaluation from 2001 to 2011 was performed. The relationship between features of portal hypertension (VAST score ≥ 2, 1 point each for Varices, Ascites, Splenomegaly or Thrombocytopenia) and a major adverse event (death, need for transplant, or hepatocellular carcinoma) was examined using logistic regression. Results 73 post-Fontan patients (30% female, 73% Caucasian, 66% systemic left ventricle (SLV), mean age 24 ± 11 years, mean interval from Fontan 17 ± 6 years) were included in analysis. Features of portal hypertension (VAST score ≥ 2) were present in 26 (36%), and there were 19 major adverse events: death (n = 12), transplant (n = 6), and HCC (n = 1). A significant relationship was found between VAST score ≥ 2 and major adverse events (OR = 9.8, 95% CI [2.9-32.7]). After adjusting for time since Fontan, SLV, age, hemoglobin and type of failure, VAST score ≥ 2 remained significant (OR = 9.1, 95% CI [1.4-57.6]). Conclusion Fontan patients with features of portal hypertension have a 9-fold increased risk for a major adverse event. Therapies targeted to manage clinical manifestations of portal hypertension, and early referral to heart transplant may help delay major adverse events. Future prospective studies are needed to confirm these findings. © 2013 Elsevier Ireland Ltd.