Long-chain omega-3 polyunsaturated fatty acids (omega-3 LCPUFA) are essential for human beings and they should be incorporated to our body through the diet. For almost a century it is known that these fatty acids are essential for growth and development of individuals andfrom 1970 onwards, investigations have found solid evidence about several health properties attributed to these fatty acids, especially at the cardiovascular, neurological and anti-inflammatory level; it is in this sense that today a large number of investigations have focused to study the protective role of omega-3 LCPUFA against cancer, primarily based on the anti-inflammatory properties that they possess. In this paper we describe a series of evidences to establish a possible preventive and therapeutic use of omega-3 LCPUFA against cancer, specifically in prostate, breast and colon cancer.