Objective: To describe the proportion of patients undergoing major abdominal surgery who develop postoperative hypothermia, and the variables associated with its occurrence. Material and Methods: We conducted a prospective cohort study in a tertiary care referral hospital in Mexico City to describe the incidence of perioperative hypothermia and factors associated with postoperative hypothermia. A repeated measures ANOVA model was used to compare preoperative, intraoperative, and postoperative temperatures. Potential variables associated with hypothermia were evaluated with a logistic regression analysis. Results: A total of 110 patients were included in the analysis. Of them, 61% (n=67) were women. The mean age was 56.7 years (SD: 16.3, range: 75). The most frequently involved organ on which surgery was performed was kidney or urinary tract (21.8%), followed by large bowel (14.5%) and exploratory laparotomy (14.5%). The incidence of postoperative hypothermia in patients undergoing major abdominal surgery was 57.3%, while preoperative and intraoperative hypothermia occurred in 55.5% and 79.1%, respectively. Age over 60 years was the only variable associated with postoperative hypothermia after multivariable adjustment for sex, age, and time surgery (OR=18.4, 95% CI:3.79-89.6, p<0.0001). Conclusion: Increasing age was the only variable associated with postoperative hypothermia in patients undergoing major abdominal surgery.