Purpose: We investigated the distribution of early clinical outcomes among normal, obese, and morbidly obese patients undergoing open heart surgery., Methods: Medical records of 1,000 patients undergoing open heart surgery since February 2011 at our hospital were investigated retrospectively after permission was obtained from the Council of Education Planning of the hospital. The comorbidities and perioperative and discharge data were analyzed for 279 patients with a body mass index (BMI) score between 18 and <30 [non-obese reference group (NRG, n = 279)]; 166 patients with BMI between 30 and <35 [obese group (OG, n = 166); and 192 seriously obese patients with BMI ≥35 [extreme obese group (EOG, n = 192)]. Distribution of the patients according to BMI scores was found to represent the BMI distribution of the Turkish population., Results: Pulmonary and infective complications were significantly higher in EOG patients compared to NRG based on crude confidence interval. Based on adjusted multiple logistic regression analysis, by adjusting the effects of age, sex, comorbidities (diabetes mellitus, hypertension, hyperlipidemia, chronic obstructive pulmonary disease), and smoking, the incidence of pulmonary and gastrointestinal complications in EOG was higher compared to NRG. Discharge with morbidity was significantly higher in OG and EOG compared to NRG., Conclusions: We found that obesity does not increase short-term mortality for open heart surgery; however, it increases the risk of postoperative pulmonary and gastrointestinal complications and discharge with morbidity.