We report the case of a 75-year-old male patient who underwent bypass surgery. Intraoperatively unstable hemodynamics with excessive arterial blood pressure was observed. This resulted in the tearing of an anastomosis, which subsequently required hemostasis for repeated bleeding. Postoperatively, laboratory findings and diagnostic imaging confirmed the diagnosis made intraoperatively of a pheochromocytoma. Any surgery without awareness of the possibility of a pheochromocytoma will dramatically increase intraoperative and postoperative morbidity and mortality, especially in cardiac surgery. The uncontrolled release of catecholamines raises arterial blood pressure which can become life-threatening and lead to serious intraoperative complications, as well as cerebrovascular and cardiac comorbidity.