Background: Postoperative temperature dysregulation affects the length of hospital stay and prognosis. This study evaluated the factors that influence the occurrence of fever in patients after aortic valve replacement surgery. Methods: Eighty-seven consecutive patients who underwent aortic valve replacement surgery were included. Patients’ age, sex and body mass index; presence of diabetes mellitus; operation time; blood loss; blood transfusion volume; preoperative and postoperative laboratory findings; presence or absence of oral function management; and fever >38°C were retrospectively analysed through univariate and multiple logistic regression analyses. Results: Among the variables, only diabetes mellitus status was significantly associated with fever ⩾38°C. Postoperatively, patients with diabetes mellitus were significantly less likely to develop fever above 38°C and a fever rising to 38°C. Conclusions: This study shows that the presence of comorbid diabetes mellitus decreases the frequency of developing fever >38°C after aortic valve replacement surgery.