A relation between inadvertent perioperative hypothermia and possible important risk factors during major abdominal surgeries was investigated. Cross-sectional descriptive study. Trakya University Hospital, Edirne, Turkey during 2016-2018. Five hundred and twenty-nine patients undergoing major abdominal surgey were divided into two groups depending on postoperative body core temperature (CTM) by the use of tympanic membrane measurement. Patients with a temperature of less than 36oC indicated hypothermia group; whereas, patients with a temperature between 36 and 37.5oC indicated normothermia group. The parameters that were considered as risk factors for hypothermia include; baseline characteristics, American Society of Anesthesiologists (ASA) status, comorbidities, operative type, duration of surgery, patient and operative room temperatures, intraoperative hemodynamic parameters, transfusion of fluids and packed red blood cells (PRBCs), labaratory data, and adverse events. Correlation between these parameters and inadvertent hypothermia was sought. A p-value of less than 0.05 was considered statistically significant. The risk factors that showed a correlation with hypothermia include: male gender, advanced age, high ASA scores, smoking, prolonged duration of operation, transfusion of fluids and PRBCs (p<0.05). In hypothermia group, duration of operation time was longer, need for transfusion was greater, hematocrit and hemoglobin values were lower than Normothermia Group of patients (p<0.05). Hypothermia was detected in 335 (63.3%) of patients. In this study, important risk factors for inadvertent hypothermia were found as; male gender, advanced age, high ASA scores, smoking, prolonged duration of operation, transfusion of fluids and/or PRBCs.