Objective To analyze the causes of unplanned overnight recovery of patients after same-day surgery and put forward countermeasures. Methods The data of same-day surgery patients in the Day Surgery Center of West China Tianfu Hospital of Sichuan University between February 2022 and May 2023 were selected. Patients who recovered overnight were defined as the unplanned overnight recovery group, and patients discharged on the same day after surgery were defined as the normal same-day group. The factors of unplanned overnight recovery after same-day surgery were analyzed. Results A total of 4 259 patients were enrolled, of whom 107 patients had unplanned overnight recovery, 4 152 patients were discharged on the same day after surgery, unplanned overnight recovery group accounted for 2.51% (107/4 259). Except for gender and age (P>0.05), there were significant differences between the two groups in the following six aspects: late starting time of surgery, longer distance from home, medical insurance settlement restrictions, pain, postoperative complications, and patient’s own factors (P<0.05). The results of logistic regression analysis showed that the late starting time of surgery [odds ratio (OR)=9.386, 95% confidence interval (CI) (2.993, 29.432), P<0.001], long distance from address [OR=4.828, 95%CI (2.015, 11.568), P<0.001], medical insurance settlement restrictions [OR=10.667, 95%CI (3.712, 30.658), P<0.001], pain [OR=30.514, 95%CI (7.688, 121.115), P<0.001], postoperative complications [OR=9.642, 95%CI (2.425, 38.342), P=0.001], and patient’s own factors [OR=16.087, 95%CI (10.358, 24.985), P<0.001] were risk factors for unplanned overnight recovery in same-day surgery patients. Conclusions The unplanned overnight recovery of same-day surgery patients in West China Tianfu Hospital of Sichuan University is related to six factors: late starting time of surgery, long distance from home, medical insurance settlement restrictions, pain, postoperative complications, and patient’s own factors. Medical staff can take corresponding measures to reduce the unplanned overnight recovery rate of same-day surgery by strict access standards, optimizing surgical scheduling, formulating individualized enhanced recovery after surgery programs, improving support for patient after discharge, and strengthening perioperative health education.