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Background: Probiotics are live microorganisms that have positive effects on the host when consumed in sufficient amounts. According to several studies, probiotics have beneficial effects on prevention and treatment of many diseases. The aim of this study was to review animal and human studies on the role of probiotics in reducing serum cholesterol, their mechanisms of action, and a brief explanation of functional probiotic foods. Materials and Methods: This review article focused on all papers indexed in scientific databases from 2000 to 2012 using the related keywords, including cardiovascular diseases, probiotics, and serum cholesterol. Results: Probiotics are used both in dairy and non-dairy products. Nowadays, the role of many probiotic strains in health is confirmed. From the studies done in this field, it can be inferred that probiotics through several mechanisms, such as binding cholesterol to cell walls of probiotics in intestine, conversion of cholesterol into coprostanol, production of short chain fatty acids, and deconjugation of bile acids, reduce serum cholesterol. Conclusion: Certain strains of probiotics have demonstrated cholesterol-lowering properties and others are under study. Further studies are needed to identify other mechanisms involved in lowering serum cholesterol and determine their safety