Coronary artery bypass grafting surgery (CABG) in hemophilia patients is challenging. Thromboelastography (TEG) is useful to assess hemostasis perioperatively. A patient with severe hemophilia A underwent CABG with TEG studies. After factor VIII (FVIII) bolus dose, TEG was normalized. Following ‘on-pump’ heparinization, protamine administration revealed prolonged TEG-R and TEG-R with heparinase confirming it, whereas the activated clotting time was normal, suggesting low FVIII activity rather than excess of heparin. Another FVIII bolus yielded complete normalization of all TEG parameters. Data are compatible with in-vitro assays performed in our laboratory, showing that both heparin and protamine may impair measurable FVIII activity. The rational use of TEG measurements enabled more accurate hemostatic therapy application with regard to FVIII, heparin and protamine administration. Adopting this approach may lead to a better therapy tailoring for hemophilia patients undergoing CABG surgery.