Background Coronary artery ostial stenosis is a rare but well-known complication to aortic root replacement. The occurrence of this complication in patients with the Medtronic Freestyle bioprosthesis is poorly described. We report a case of late bilateral coronary ostial stenosis due to pseudointimal membranes within a Medtronic Freestyle bioprosthesis, resulting in acute coronary syndrome. Case summary In 2013, a 43-year-old male patient received a Medtronic Freestyle bioprosthesis as a full aortic root implantation due to endocarditis with root abscess. Preoperative coronary angiography was normal. The patient, who had no previous symptoms of coronary ischaemia, presented with severe chest pain and acute coronary syndrome in 2017. Coronary angiography and electrocardiogram-gated contrast-enhanced cardiac computed tomography showed bilateral coronary ostial stenosis. The patient was successfully treated with coronary artery bypass grafting. Intraoperative inspection revealed pseudointimal membranes covering the coronary ostia. Histology showed fibrointimal thickening with areas of inflamed granulation tissue. Discussion Bilateral coronary ostial stenosis is a severe, potentially life-threatening condition, and a possible complication to implantation of the Medtronic Freestyle bioprosthesis as a full root. The phenomenon may occur late and should be distinguished from arteriosclerotic coronary artery disease.