A 30-year-old woman experienced severe abdominal pain 8 days after vaginal delivery. The patient was diagnosed with hemoperitoneum due to rupture of the left uterine artery pseudoaneurysm, which was confirmed via ultrasound with color Doppler and computed tomography scans. This patient was treated with bilateral uterine artery embolization to maintain fertility. A uterine artery pseudoaneurysm that causes delayed postpartum hemorrhage can occur after cesarean section or vaginal delivery. A uterine artery pseudoaneurysm can be fatal, so its detection and diagnosis are critical. Herein, we report a case of delayed postpartum hemoperitoneum due to uterine artery pseudoaneurysm rupture.