OBJECTIVE Persistent pleural effusions are a major source of morbidity after univentricular repair. These are often refractory to conventional conservative therapy. We adopted a strategy of diaphragmatic fenestration (DF) in such patients and report the results. METHODS Between January 2002 and 2014, we performed DF in 12 patients using an original technique that was first described by us. The medical records of all these patients were studied. Preoperative characteristics, amount and duration of effusions, and time to removal of chest tubes following DF were studied. RESULTS Mean age was 101 ± 57.9 months (range: 38-180 months), and mean body weight was 18.8 ± 5.8 kg (range: 11-28 kg). Five had a bidirectional Glenn, four had lateral tunnel Fontan, and three had an extracardiac Fontan as initial procedure. The average pleural drainage prior to DF was 352.5 ± 152 mL/24 h (18.75 mL/kg/24 h) for a median period of 33 days (bidirectional Glenn 216 ± 85 mL/24 h [16.5 mL/kg/24 h] for 30 days and total cavopulmonary connection 450 ± 104 mL/24 h [22.5 mL/kg/24 h] for 36 days). All patients underwent DF. Additionally, five patients underwent thoracic duct ligation on the left side. Postoperative chest drainage after DF was 25 mL/d for a median of 4 days, and the chest tubes could be removed in a median of 5.5 days (mean 7 days). There were no complications related to DF. CONCLUSIONS In patients with persistent pleural effusions following univentricular palliation, DF is an attractive option when conventional therapies have failed. This original technique of DF is simple, reproducible, cost-effective, and free of any known complications.