Abstract Objectives Liver disease is an important contributor to morbidity and mortality in patients after Fontan surgery. There has been no large-scale survey of liver health in this population. We sought to explore the prevalence and predictors of liver disease in a multicenter cohort of adults with Fontan physiology. Methods Subjects were recruited from 6 adult congenital heart centers. Demographics; clinical history; and laboratory, imaging, and histopathology data were obtained. Results Of 241 subjects (median age 25.8 years 11.8-59.4, median time since Fontan 20.3 years 5.4-34.5), more than 94% of those who underwent testing (208 of 221) had at least 1 abnormal liver-related finding. All hepatic imaging (n = 54) and liver histology (n = 68) was abnormal. Subjects with abnormal laboratory values had higher sinusoidal fibrosis stage (2 vs 1, P  = .007) and higher portal fibrosis stage (3 vs 1, P  = .003) compared with those with all normal values. Low albumin correlated with lower sinusoidal fibrosis stage (1 vs 2; P  = .02) and portal fibrosis stage (0 vs 3, P  = .002); no other liver studies correlated with fibrosis. Regenerative nodules were seen on 33% of histology specimens. Conclusions Regardless of modality, findings of liver disease are common among adults with Fontan circulation, even those appearing clinically well. Cirrhosis is present in up to one-third of subjects. Correlations between hepatic fibrosis stage and clinical history or findings on noninvasive testing are few. Further research is needed to identify patients at risk for more severe liver disease and to determine the best methods for assessing liver health in this population.