IMPORTANCE: Postpartum uterine contraction pain manifests as a severe, intermittent lower abdominal discomfort caused by uterine contraction during the early puerperium. Transcutaneous auricular vagus nerve stimulation (taVNS) has demonstrated promising effects in managing both acute and chronic pain conditions; however, there remains a paucity of studies regarding the use of taVNS for alleviating postpartum uterine contraction pain. OBJECTIVE: To investigate the effect of taVNS in alleviating postpartum uterine contraction pain among women receiving combined spinal-epidural anesthesia for elective cesarean delivery. DESIGN, SETTING, AND PARTICIPANTS: This randomized clinical trial was conducted from April 6 to August 31, 2024, at the Affiliated Hospital of Xuzhou Medical University, Xuzhou, China. Participants were aged 18 years or older and scheduled for elective cesarean delivery. Statistical analysis was performed in September 2024. All analyses were conducted according to the intention-to-treat principle. INTERVENTIONS: Participants were randomly allocated 1:1 to either the active taVNS group or the sham taVNS group. Both groups received the stimulation for 30 minutes each time, once a day, on the day of surgery and postoperative days 1 and 2. MAIN OUTCOMES AND MEASURES: The primary outcome was the incidence of moderate to severe postpartum uterine contraction pain on the third postoperative day, evaluated using a visual analogue scale (uterine contraction pain was classified as moderate to severe if the score was ≥4). Secondary outcomes included peak uterine contraction pain and incision pain, postpartum anxiety, postpartum depression, postpartum recovery quality, and sleep quality. RESULTS: A total of 156 women were recruited and randomized to the active taVNS group (78 patients; mean [SD] age, 31.5 [4.3] years) or the sham taVNS group (78 patients; mean [SD] age, 31.3 [4.5] years). The incidence of moderate to severe uterine contraction pain in the active taVNS group was 5.1% (4 of 78) compared with 28.2% (22 of 78) in the sham taVNS group on the third postoperative day (relative risk, 0.18 [95% CI, 0.07-0.50]; P < .001) The active taVNS group had lower median scores on the third postoperative day for incisional pain (visual analogue score: 2.20 [IQR, 2.00-2.50] vs 3.00 [IQR, 2.60-3.33]), depression (EPDS: 3.00 [IQR, 2.00-4.00] vs 5.00 [IQR, 3.00-6.00]), and anxiety (PRAQ-R2: 13.50 [IQR, 12.00-15.00] vs 15.00 [IQR, 13.75-17.00]), as well as significantly higher scores for recovery quality on the third postoperative day (ObsQoR-11: 104 [IQR, 103-105] vs 99 [IQR, 96-101]) and sleep quality on the second postoperative day (LSEQ: 52.00 [IQR, 50.00-55.00] vs 47.50 [IQR, 43.00-52.00]) compared with the sham taVNS group. CONCLUSIONS AND RELEVANCE: In this randomized clinical trial, taVNS significantly reduced uterine contraction pain, incisional pain, depression, and anxiety, and improved recovery quality and sleep quality compared with sham taVNS. These findings suggest that taVNS represents a novel and safe strategy for alleviating postpartum uterine contraction pain among women undergoing cesarean delivery and for promoting postoperative recovery. TRIAL REGISTRATION: Chinese Clinical Trial Register Identifier: ChiCTR2400082716.