Key Clinical MessageIn hemophilia patients undergoing cardiac surgery, ROTEM® and Quantra® viscoelastic tests are useful to monitor perioperative hemostatic status and a single dose of rIX‐FP is safe and avoids any hemorrhagic or thrombotic complication.AbstractCardiac surgery poses a high hemostatic risk in patients with hemophilia. We present the first case of an adult patient with hemophilia B on treatment with albutrepenonacog alfa (rIX‐FP) who underwent surgery for acute coronary syndrome. Treatment with rIX‐FP made it possible to perform the surgery safely.