Fatty acids derived from fish oil are long-chain omega-3 (n-3) polyunsaturated fatty acids. The important polyunsaturated fatty acids of fish oil are eicosapentaenoic acid, and docosahexaenoic acid. For decades, there has been a debate about the use of omega-3 fatty acids and their benefits on cardiovascular health. The more recent trials including the JELIS, VITAL, STRENGTH, and ASCEND trials, addressed the paucity of data of omega-3 fatty acids on primary and secondary prevention of cardiovascular events and the risk-benefit balance of these supplements. Prior to these studies, many large randomized controlled trials have shown conflicting results on the effect of polyunsaturated fatty acids in patients with prior coronary artery disease, stroke, or major vascular events. These inconsistent results warrant a better understanding of the effects of omega-3 fatty acids on the subtypes of cardiovascular diseases, and their use in primary and secondary prevention. More recently, icosapent ethyl showed a significant reduction in cardiovascular mortality and ischemic events in patients with elevated triglyceride (TG) and established cardiovascular disease or diabetes. The REDUCE-IT trial paved the way to further reduce cardiovascular risk in patients with high TG despite being on a maximally tolerated statin. The aim of this review is to discuss these recent updates on the use of various forms of fish oil, including prescription form and supplement in cardiometabolic diseases, and their surrounding controversies. Copyright © 2019 Elsevier Inc. All rights reserved.