This review focuses on and discusses the primary phytochemicals present in microalgal biomass - carotenoids, phenolic compounds, antioxidant vitamins, sterols, and polyunsaturated fatty acids - and also on the exopolysaccharides, which are produced by some types of microalgae and may play a significant role in the prevention of cardiovascular diseases (CVD) and strokes. We have listed several preclinical trials and clinical studies supporting the health benefits that most of these compounds may provide. Microalgae are very easy to grow and are not vulnerable to contaminants when grown under controlled conditions. Proper handling and growth conditions may improve the production of phytochemicals. Therefore, they may represent an excellent source of nutraceuticals and food supplements once their safety as a food supplement has been confirmed.