•Postpartum uterine contraction pain is common and severe in some women.•Multiparous women experience more intense postpartum uterine contraction pain.•Women with dysmenorrhea have a higher risk of postpartum uterine contraction pain.•Breastfeeding exacerbates uterine contraction pain in the early postpartum period. Postpartum uterine contraction pain has not been studied sufficiently. We aimed to assess the incidence, intensity, and risk factors for postpartum uterine contraction pain. Women with singleton pregnancies who delivered vaginally were enrolled in this prospective, observational, single-institution study. We determined the numerical rating scale (NRS) score (0 to 10-point) for uterine contraction pain at 6, 12, 24, and 48 h after delivery. Generalized mixed modeling was used to identify the risk factors for significant postpartum uterine contraction pain (NRS score ≥3). We compared the incidence and severity of postpartum uterine contraction pain between nulliparous and multiparous women. Two hundred and sixty-five nulliparous and 139 multiparous women were included. Forty-seven percent (188/404; 95% confidence interval CI 41.7% to 51.4%) of women presented with significant uterine contraction pain within 48 h of delivery. The generalized mixed model showed that nulliparous women had a lower risk of significant postpartum uterine contraction pain compared with multiparous women (odds ratio OR 0.33, 95% CI 0.17 to 0.61; P<0.001). Women with a history of dysmenorrhea had higher risk of significant postpartum uterine contraction pain (OR 1.77, 95% CI 1.12 to 2.79; P=0.014). Both nulliparous and multiparous women reported more intense uterine contraction pain while breastfeeding (P<0.001). Postpartum uterine contraction pain is common and severe in some women. Parity and history of dysmenorrhea are significant risk factors for significant postpartum uterine contraction pain.