Objective: This study aimed to investigate the rate of prolonged postoperative ileus (PPOI) and its predictive factors focusing on age, body mass index, smoking status, postoperative mobilization, and preoperative anxiety and depression among patients undergoing major gastrointestinal surgery.Materials and Methods: This prospective observational study included patients who underwent elective major gastrointestinal surgery in a super tertiary hospital in Thailand. The data were collected using a uniform case record form including the Hospital Anxiety and Depression Scale and Fagerstrom Test for Nicotine Dependence. PPOI was defined using criteria of Vather et al. (2013). Predictive factors for PPOI were determined by multivariate analysis.Results: A total of 123 patients were enrolled, with an average age of 59.8 ± 12.7 years. The most common indication for surgery was gastrointestinal malignancy (96 patients, 78%), followed by an open approach (75 patients, 61%) and a combined general and epidural anesthesia (58 patients, 47%). Approximately 30% of patients had a history of smoking. Preoperative anxiety and depression were equally found in nine patients (7%). Twenty-seven patients (22%) experienced PPOI. The significant predictive factors of PPOI were having preoperative anxiety (OR = 6.26, 95% CI = 1.22–44.41, p = 0.046) and being unable to ambulate on postoperative day 1 (OR = 3.26, 95% CI = 1.25–8.50, p = 0.015).Conclusion: Preoperative anxiety and delayed postoperative ambulation were two predictors for PPOI in this study. Some interventions to reduce preoperative anxiety and encourage early postoperative ambulation should be considered in patients undergoing major elective gastrointestinal surgery.