Perforations of saphenous venous grafts during coronary angioplasty are rare and potentially lethal. The objective of this clinical case report is to highlight this unusual complication and necessary treatment. A 76-year-old woman, 3 months after coronary artery bypass grafting (left internal mammary artery to left anterior descendant artery, saphenous vein graft to obtuse marginal, saphenous vein graft to right coronary artery), demonstrated typical signs of acute coronary syndrome. Coronary angiogram revealed, inter alia, two critical lesions in saphenous vein graft to right coronary artery. Percutaneous coronary intervention was performed with placement of two drug-eluting stents, complicated by a vessel rupture and heavy extravasation of contrast. A polyurethane-covered stent was then deployed and successfully sealed the vascular wall. In a computed tomography of the chest, a mediastinal haematoma near the heart base and right heart margin was found. Subsequently, this intrathoracic bleeding caused external impression on saphenous vein graft to right coronary artery, leading to near occlusion of the vessel with recurrence of chest pain and ST-segment elevation in inferior wall electrocardiogram leads. Immediate coronary angiography and drug-eluting stent implantation was performed. During, further, in-hospital follow-up, patient was free of chest pain; computed tomography scan performed after 10 days revealed regression of haematoma. Clinicians must remain alert to the potential of life-threatening complications associated with saphenous venous graft angioplasty, as their recognition is critical to institution of prompt, appropriate therapy.