Objective <p>Gastrointestinal complications and acute pancreatitis after cardiac surgery are relatively rare; however, they may sometimes progress to serious conditions and can be challenging to manage. We aimed to investigate the association between lower-body circulatory arrest (LCA) time under mild-to-moderate hypothermia with antegrade selective cerebral perfusion (ASCP) and postoperative visceral complications in patients undergoing thoracic aortic surgery.</p> Methods <p>We retrospectively analyzed 221 patients who underwent thoracic aortic surgery for degenerative aneurysms involving the ascending aorta and aortic arch with LCA under mild-to-moderate hypothermia between 2015 and 2025. The associations between LCA time and postoperative complications, including gastrointestinal complications and pancreatitis, were evaluated using logistic regression analyses.</p> Results <p>Prolonged LCA time was significantly associated with an increased incidence of postoperative gastrointestinal (<i>P</i> = 0.006) and lung complications (<i>P</i> = 0.02) in logistic regression models adjusted for minimal temperature. A similar trend was observed for AKI without statistical significance (<i>P</i> = 0.08). In contrast, acute pancreatitis was not associated with LCA time. Within the studied temperature range, minimal temperature was not significantly associated with visceral complications.</p> Conclusions <p>Prolonged LCA time under mild-to-moderate hypothermia using ASCP was significantly associated with increased postoperative gastrointestinal and lung complications, whereas pancreatitis was not associated. The duration of lower-body ischemia may be an important determinant of visceral organ injury within the studied temperature range.</p>