This narrative review evaluates whether the creation or maintenance of a fenestration during Fontan completion influences long term outcomes in patients with single-ventricle physiology, including overall survival, freedom from Fontan failure, arterial oxygen desaturation, thromboembolic complications, and Fontan-associated liver disease. The screening process yielded 9 studies for narrative synthesis, including 8 primary studies and 1 meta-analysis. Across original studies, fenestration was not associated with a significant difference in overall survival or freedom from Fontan failure compared with non-fenestrated Fontan circulation or later fenestration closure. The most consistent long-term finding was persistent arterial oxygen desaturation in patients with an open fenestration, whereas evidence regarding thromboembolic events and Fontan-associated liver disease was mixed and requires cautious interpretation. Current evidence therefore suggests that Fontan fenestration should primarily be regarded as a strategy to reduce early postoperative morbidity rather than an intervention that reliably improves long-term survival or prevents late Fontan failure.