Large symptomatic mediastinal seroma following modified-BT shunts, traditionally required revisional thoracotomy. We describe percutaneous image-guided pigtail catheter drainage in the successful treatment of early mediastinal seroma secondary to PTFE Blalock-Taussig shunt, avoiding thoracotomy. A retrospective review of all relevant clinical and imaging records in five patients was performed. All five presented with intermittent stridor, respiratory distress and/or episodic desaturation within 6 weeks of their surgery. In four of five infants, percutaneous drainage was effective and reoperation was avoided. In one of five, rather than urgent surgical evacuation and BT shunt revision, we were able to perform an elective stage-II bidirectional Glenn SVC-RA anastamosis in a stable infant. There were no complications. Percutaneous image-guided drainage of mediastinal seroma secondary to PTFE-BT shunt is a safe, minimally invasive, and effective treatment. This may avoid BT shunt revision.