Major dietary sources of omega-3 fatty acids are fish containing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), as well as nuts, seeds, and vegetable oils containing α-linolenic acid (ALA). Omega-3 fatty acids, especially those derived from marine sources, may be a useful tool for the primary and secondary prevention of cardiovascular disease. Omega-3s exert their cardioprotective effects through multiple mechanisms, including reducing arrhythmias and altering production of prostaglandins, which reduces inflammation and improves platelet and endothelial function. To date, no serious adverse effects of omega-3s have been identified, despite extensive study. In adults, any potential harm from mercury exposure from consuming fish rich in omega-3s is outweighed by the proven cardiovascular benefits of eating fish. Concerns over increased bleeding complications have not materialized despite the increased concomitant use of aspirin and clopidogrel. We recommend one serving (200-400 g) of fatty fish two times per week and a diet that includes foods rich in ALA for the primary prevention of cardiovascular disease. We recommend one serving (200-400 g) of fatty fish or a fish oil supplement containing 900 mg of EPA + DHA every day and a diet rich in ALA for patients with known cardiovascular disease or congestive heart failure.