Epidemiology studies suggest that the consumption of diets rich in flavonoids is associated with reduced risk of cardiovascular disease. Plant-derived foods and beverages, such as red wine, tea, grape and grape juice, cocoa and chocolate, can be rich in 1 particular class of flavonoid, the flavan-3-ols. There is now an increasing body of research that suggests that consuming flavanol-rich foods can positively affect hemostasis, through mechanisms that either directly affect platelet function or increase certain endothelium-derived factors that maintain platelet acquiescence or increase fibrinolysis. In this paper, we will review a series of in vivo studies on the effects of flavanol-rich cocoa and chocolate on platelet activation and platelet-dependent hemostasis. In addition, we will briefly review the body of literature with regard to other flavanol-rich foods and beverages, and possible mechanisms of action.