Introduction: Acute pain is a common complication following cesarean section under general anesthesia. Post-cesarean section pain management is important for both the mother and the newborn. This study compared the effects of patient-controlled intravenous analgesia (PCIA) using sufentanil or tramadol on postoperative pain control and initiation time of lactation in patients who underwent cesarean section under general anesthesia. Methods: Primiparas (n=146) scheduled for cesarean section under general anesthesia were randomized to receive PCIA with sufentanil or tramadol. Movement-evoked and rest-pain intensity were assessed by the Numerical Rating Scale (NRS) postoperatively. The number of PCIA attempts, amount of drug consumed, initiation time of lactation, and Quality of Recovery Score 40 (QoR-40) were recorded at 4, 8, 12, and 24 h postoperatively. Pre- and postoperative serum prolactin levels were recorded. Results: No between-group difference existed in the NRS at rest at any time point postoperatively. Patients on sufentanil had more movement-evoked pain and a higher sedation score at 4, 8, and 12 h postoperatively, as compared with the tramadol group. At 24 h, the QoR-40 was higher in the tramadol group compared with the sufentanil group. No significant between-group differences were present in patient satisfaction and nausea/vomiting scores. Postpartum prolactin levels were significantly higher in the tramadol group versus the sufentanil group, corresponding with a significant delay in initiation of lactation in the latter. Conclusion: PCIA with tramadol may be preferred due to lower movement-evoked pain, higher quality of recovery, and earlier lactation in patients following cesarean section under general anesthesia.