Heart failure is associated with increased risk of venous thromboembolism, stroke, and sudden death. Platelet abnormalities have been well described in heart failure but the significance of platelets in contributing to the thromboembolic complications of heart failure remains uncertain. Furthermore, the role of antiplatelet agents in heart failure remains unclear. This review will focus on platelet activation and the role of platelet dysfunction in heart failure, with particular regard to pathophysiology and outcome. The effects of heart failure therapeutics on platelet function and antiplatelet therapy in heart failure will also be discussed.