Plastic bronchitis (PB) and protein-losing enteropathy (PLE) are rare but potentially devastating complications of the Fontan circulation. PB occurs in ∼4% of Fontan patients, typically presents within 2 to 3 years of Fontan completion with chronic cough, wheezing, fever, or acute asphyxiation, and is characterised by proteinaceous airway casts that are expectorated or found on bronchoscopy. PLE develops in 4% to 13% of patients, usually within 5 to 10 years post Fontan, and manifests with edema, ascites, hypoalbuminemia, lymphopenia, hypogammaglobulinemia, and elevated fecal alpha-1 antitrypsin 1. These disorders have similar pathophysiology involving disruption of the lymphatic system resulting from elevated central venous pressure combined with elevated lymphatic production and inflammation, resulting in lymphatic drainage into low-pressure circuits such as the airways (PB) and duodenum (PLE). Our understanding of these disorders has greatly improved over the past decade as a result of advances in imaging of the lymphatic system through magnetic resonance lymphangiography and early success with lymphatic interventions including lymphatic embolisation, thoracic duct embolisation, and percutaneous thoracic duct decompression. Both PB and PLE require a multidisciplinary approach that addresses and optimises residual hemodynamic lesions through catheter-based intervention, lowers central venous pressure through medical therapy, minimises symptoms, and targets abnormal lymphatic perfusion when symptoms persist. This review summarises the pathophysiology of these disorders and the current evidence base regarding management, proposes treatment algorithms, and identifies future research opportunities. Key considerations regarding the development of a lymphatic intervention program are also highlighted.