AbstractBackground/AimsAlthough colonic diverticular bleeding (CDB) is common, few reports have described the effects of antithrombotic agents (ATs) on CDB. This study aimed to clarify the risk factors of re‐bleeding within a year in CDB patients.MethodsWe retrospectively analyzed the risk of re‐bleeding in CDB patients. Among 324 patients who were hospitalized for acute lower gastrointestinal bleeding at our institution during the period from 2015 to 2019, we used 76 patients who were diagnosed as CDB. Risk factors for re‐bleeding were determined by Cox proportional hazard models.ResultsOf 76 patients analyzed, 32 were taking ATs, nine of whom were taking multiple agents. Twenty‐six patients re‐bled within a year. Compared with the patients without re‐bleeding, patients with re‐bleeding within a year had been treated by antithrombotic therapy more frequently (62% vs. 32%, p = 0.013). Cox proportional hazard model revealed that treatment with ATs (hazard ratio 3.89, 95% confidence interval 1.53–10.74, p = 0.004) was an independent risk factor for re‐bleeding within a year.ConclusionATs were found to be an independent risk factor related to re‐bleeding within a year in patients with CDB.