Background: Open heart surgery is a type of extracorporeal circulation used during surgery to keep the patient's blood and oxygen flowing. It temporarily substitutes the function of the heart and lungs. Aim of the study: To determine the risk factors and complications of patients undergoing open heart surgery. Research design: A descriptive research design was used in this study. Setting: Cardio-thoracic intensive care unit at Assuit University Heart Hospital. Sample: A convenience sample of 60 adult patients was involved in the study. Tools: Tool one: patient's assessment questionnaire; tool two: Patient evaluation tool of open heart surgery assessment questionnaire. Results: about 50% of risk factors of the studied patients were old age, as 45% had smoked, and hypertension had an increased complications of open heart surgery. The current study revealed a positive correlation between acute renal failure, hemorrhage, infection and age. Conclusion: Advanced age was considered the first risk factors for the occurrence of complications followed by hypertension and smoking. Recommendations: Develop intraoperative guidelines to reduce the systemic inflammatory response syndrome (SIRS) by decreasing the time of operation, maintain appropriate glucose levels and monitoring intraoperative fluid balance and hematocrit levels to help to reduce the incidence of postoperative complications.