Background: To investigate factors associated with risk for rebleeding and 30-day mortality following prophylactic transarterial embolization in patients with high-risk peptic ulcer bleeding. Methods: We retrospectively reviewed medical records and included all patients who had undergone prophylactic embolization of the gastroduodenal artery at Rigshospitalet, Denmark, following an endoscopy-verified and treated peptic Sulcer bleeding, from 2016 to 2021. Data were collected from electronic health records and imaging from the embolization procedures. Primary outcomes were rebleeding and 30-day mortality. We performed logistical regression analyses for both outcomes with possible risk factors. Risk factors included: active bleeding; visible hemoclips; Rockall-score; anatomical variants; standardized embolization procedure; and number of endoscopies prior to embolization. Results: We included 176 patients. Rebleeding occurred in 25% following embolization and 30-day mortality was 15%. Not undergoing a standardized embolization procedure increased the odds of both rebleeding (odds ratio 3.029, 95% confidence interval (CI) 1.395–6.579) and 30-day overall mortality by 3.262 (1.252–8.497). More than one endoscopy was associated with increased odds of rebleeding (odds ratio 2.369, 95% CI 1.088–5.158). High Rockall-score increased the odds of 30-day mortality (odds ratio 2.587, 95% CI 1.243–5.386). Active bleeding, visible hemoclips, and anatomical variants did not affect risk of rebleeding or 30-day mortality. Reasons for deviation from standard embolization procedure were anatomical variations, targeted treatment without embolizing the gastroduodenal artery, and technical failure. Conclusions: Deviation from the standard embolization procedure increased the risk of rebleeding and 30-day mortality, more than one endoscopy prior to embolization was associated with higher odds of rebleeding, and a high Rockall-score increased the risk of 30-day mortality. We suggest that patients with these risk factors are monitored closely following embolization. Early detection of rebleeding may allow for proper and early re-intervention. Graphical abstract: (Figure presented.)