Background: Parallel to the advanced surgical techniques, the critically ill postoperative surgical patients are increasing in intensive care units (ICU). Mortality and morbidity of these patients in ICU are multifactorial. However, which of them is most effective is not clearly understood. Objective: The aim of this study is to evaluate the factors, which more frequently affect mortality and morbidity of the critically ill patients in postoperative period. Methods: Between 2011-2012, 121 patients were included in this study. Postoperative surgical patients, who followed-up in our ICU during one year period, were evaluated in respect of demographic characteristics, “American Society of Anesthesiologists” (ASA) physical status, preexisting co-morbidities, data about surgical procedures, “Acute Physiology and Chronic Health Evaluation” (APACHE) II scores, hemoglobin and hematocrit levels, the amount of transfusion, duration of mechanical ventilation, length of stay in ICU, vasopressor agent requirements and the effects of these parameters on mortality and morbidity of the patients were examined. Results: We found that age, gender, ASA physical status, co-morbidities, hemoglobin and hematocrit levels on admission, blood loss in the intraoperative period and operation time were not predictive factors on mortality. However, APACHE II≥25, the amount of transfusion, co-morbidities developed in ICU, mechanical ventilation more than 3 days, length of stay more than 6 days, need of vasopressor agents were risk factors on mortality. Logistic regression analysis showed blood transfusion, co-morbidities developed in ICU and prolonged length of stay were independent risk factors for mortality. Conclusions: In conclusion, we want to emphasize the importance of preventive strategies and precision of blood transfusion in critically ill surgical patients because of the deteriorated effects of co-morbidities developed in ICU resulted in prolonged length of stay and mortality.