This tertiary centre study aims to identify factors associated with adverse outcomes in adult survivors with total cavopulmonary connection (TCPC) Fontan palliation for single ventricle. This retrospective review of medical records identified adult (≥18 years) survivors of TCPC Fontan palliation who were followed at a single tertiary centre between 1 January 2000 and 1 July 2019. Adverse outcomes were defined as arrhythmia, pacemaker/implantable cardioverter defibrillator placement, liver cirrhosis, protein losing enteropathy, hospitalisation for heart failure, thromboembolic complication and/or death. 160 adult TCPC patients met the inclusion criteria: 117 (73.1%) extracardiac and 43 (26.9%) lateral tunnel. The median (IQR) duration of follow-up since TCPC palliation was 17.5 (11.8-21.3) years. An adverse outcome occurred in 87 (54.4%) patients. Adverse outcome-free survival rates at 10, 20 and 25 years post TCPC were 89% (95% CI 82% to 93%), 60% (95% CI 50% to 69%) and 24% (95% CI 15% to 35%), respectively. On multivariate analysis, extracardiac Fontan (HR 2.21, 95% CI 1.20 to 4.08, p=0.011) was observed to be an independent risk factor for adverse outcomes after adjusting for age, race, morphology of the systemic ventricle and history of fenestration. In this single-centre retrospective study of adult survivors of TCPC palliation, extracardiac Fontan was associated with an increased hazard for adverse outcomes. This finding could guide clinicians in developing risk modification strategies and management decisions to improve long-term outcomes in these patients. © Author(s) (or their employer(s)) 2022. No commercial re-use. See rights and permissions. Published by BMJ.