Successful management of surgery in severe coagulation disorders depends on adequate replacement of the deficient factors from intervention until wound healing. Extended half-life (EHL) recombinant factor IX (rFIX) has been increasingly used in hemophilia B (HB) patients. Monitoring of blood levels of EHL rFIX allows to obtain pharmacokinetic (PK) parameters in order to optimize and personalize therapeutic scheme. We describe a case of a young male with severe HB who successfully underwent aortic valve repair. This is the first reported open-heart surgery in a patient with severe HB using EHL rFIX. The success was based on accurate PK evaluation and on meticulous preoperative planning and close cooperation among surgeons, hemophilia specialists, and laboratory team despite the long distance between hemophilia center and surgical clinic.