Objective To investigate the predictors of severe postpartum hemorrhage (sPPH) in patients with placenta accreta spectrum disorders (PAS) without a history of cesarean delivery (CD). Design Retrospective case-control study. Setting A referral center for high-risk obstetrical patients in China. Population Patients with PAS (the 2019 International Federation of Gynecology and Obstetrics clinical diagnostic criteria) without a history of CD. Methods Patients were categorized into the sPPH and non-sPPH groups based on whether the postpartum bleeding volume within 24 hours after delivery exceeded 1500 mL. Univariate, multivariate and decision tree analyses were performed to identify predictors of sPPH in PAS without a history of CD. Main Outcome Measures Postpartum bleeding volume within 24 hours after delivery. Results This study included 348 patients without a history of CD, 60 of whom experienced sPPH. Multivariate analysis identified vaginal delivery (adjusted odds ratio [aOR] 15.486, 95% confidence interval [CI] 4.013–59.767), placenta previa (aOR 3.215, 95% CI 1.257–8.222), a history of three or more intrauterine procedures (aOR 2.433, 95% CI 1.129–5.244), and multiparity (aOR 2.120, 95% CI 1.070–4.202) as independent predictors of sPPH in this patient population. Conclusion Patients with PAS without a history of CD have distinctive predictors of sPPH. Besides placenta previa, a history of three or more intrauterine procedures and multiparity warrant close monitoring to prevent sPPH. Vaginal delivery should be discouraged in patients with PAS without a history of CD.