This study evaluated the efficacy of fibrin glue for preventing postendoscopic submucosal dissection (ESD) bleeding in high-risk patients for bleeding (expected iatrogenic ulcer size ≥40 mm or receiving antithrombotic therapy). A multicenter, open-label, randomized controlled trial was performed at 4 tertiary medical centers in South Korea between July 1, 2020, and June 22, 2022. Patients with gastric neoplasm and a high risk of post-ESD bleeding were enrolled and allocated at 1:1 to a control group (standard ESD) or a fibrin glue group (fibrin glue applied to iatrogenic ulcers after standard ESD). The primary outcome was overall bleeding events within 4 weeks. The secondary outcomes were acute bleeding (within 48 hours post-ESD) and delayed bleeding (48 hours to 4 weeks post-ESD). In total, 254 patients were randomized, and 247 patients were included in the modified intention-to-treat population (125 patients in the fibrin glue group and 122 patients in the control group). Overall bleeding events occurred in 12.0% (15/125) of the fibrin glue group and 13.1% (16/122) of the control group ( P = 0.791). Acute bleeding events were significantly less common in the fibrin glue group than in the control group (1/125 vs 7/122, P = 0.034). Delayed bleeding events occurred in 11.2% (14/125) in the fibrin glue group and 7.3% (9/122) in the control group ( P = 0.301). This trial failed to show a preventive effect of fibrin glue on overall post-ESD bleeding in high-risk patients. However, the secondary outcomes suggest a potential sealing effect of fibrin glue during the acute period.