Percutaneous upsizing of surgically placed Blalock–Taussig shunts is an uncommon practice. We report the case of an 8-month-old infant with single-ventricle physiology, who – due to comorbidities – was deemed unsuitable to proceed with Glenn operation. The 3.5-millimetre Blalock–Taussig shunt was stented successfully with a 5-millimetre pre-mounted stent, resulting in an increase in shunt diameter and oxygen saturation by nearly 30% and 10%, respectively.