Background: Placenta accreta spectrum can cause catastrophic hemorrhage. Knotless barbed suture line has been considered to reduce bleeding during cesarean section (CS). The purpose of this study was to determine whether the use of knotless barbed suture line could effectively reduce bleeding in patients with placenta accreta and placenta increta. Methods: After obtaining ethical approval, we performed a retrospective cohort study between women with the barbed suture (n = 42) and no barbed suture (control, n = 42). In the barbed suture group, the bleeding site from the damaged myometrium layer caused by the placenta villous invasion was sutured by barbed line with a continuous running suture made in the myometrium layer. In the control group, the uterine incision was repaired with two layers of a continuous suture using the conventional polyglactin suture line. Primary outcomes were the blood loss during the CS and blood loss in the first 24 hours after surgery. Results: The total sample size was 84 (42 in the barbed suture group, another 42 in the control group). Blood loss during CS was significantly lower than the control group by an average of approximately 200 mL (848.57 \pm 373.20 mL in the barbed suture group vs. 1055.95 \pm 470.88 mL in the control group, p = 0.028). Blood loss during the first 24 hours was also diminished in the barbed suture group (42.70 \pm 36.71 mL in the barbed suture group vs. 65.60 \pm 61.44 mL in the control group, p = 0.041). Conclusions: The application of barbed suture line reduced blood loss both during CS and after 24 hours of CS.