Heparin is a preferred initial anticoagulant in patients with new-onset atrial fibrillation (AF). Despite continuous debate about the risk, there has been a concern about heparin-induced hemorrhagic pericarditis and cardiac tamponade. We present a case of a new onset atrial fibrillation (AF) in a patient with renal impairment and evidence of pericardial effusion complicated by hemopericardium development after starting anticoagulation. Although the risk of hemorrhagic conversion of uremic pericarditis induced by heparin in ESRD patients with new onset AF was suggested in the literature, this case raises the possibility of a similar complication in dialysis-associated pericarditis. Therefore, we aim to heighten alertness regarding this potential complication of a commonly used medication in clinical practice. We also aim to review the current anticoagulation recommendations in this setting.