Constipation has been reported to increase the risk of cardiovascular mortality. Patients with atrial fibrillation (AF) and heart failure (HF) have more comorbidities and an increased bleeding risk. However, it remains unclear whether constipation is associated with an increased risk of incident bleeding complications in AF with HF. Here, we investigated the association between constipation requiring laxatives and major bleeding in AF and HF. We retrospectively analyzed the medical records of 370 consecutive patients hospitalized for AF and congestive HF. Constipation was defined as regularly taking laxatives or having at least two prescriptions for a ≥ 30-day supply of laxatives. Sixty patients experienced major bleeding events during a median follow-up of 318 days. The most common sites of bleeding were lower gastrointestinal (28%, 17/60), upper gastrointestinal (27%, 16/60), and intracranial (20%, 12/60). There were 33 (55%) patients with constipation in the bleeding group and 107 (35%) in the non-bleeding group (P= 0.004). Multivariate Cox regression analysis adjusted for HAS-BLED score, hemoglobin, and direct oral anticoagulant use showed that constipation (hazard ratio [HR] 1.85, 95% confidence interval [CI] 1.11–3.08;p= 0.019) was a significant risk factor for major bleeding. We found a significant association between constipation requiring laxatives and major bleeding in patients with AF and HF. These findings indicate the need for constipation prevention in these patients to avoid reliance on invasive defecation management, including laxatives.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00380-023-02249-6.