Breast cancer is recognized as one of the most common cancers worldwide that can lead to death. Alternative treatment options are needed due to drug resistance caused by current treatment methods such as chemotherapy, inclusion of healthy cells in the target, and possible side effects. In this context, there is great interest in natural compounds and their active metabolites. One of these is flaxseed (FS), which is one of the most studied foods to be associated with breast cancer. FS is a functional food with high nutritional value. FS components (fatty acids, fiber, and lignans) and especially the basic lignan structure in FS content, secoisolariciresinol diglucoside (SDG) and its metabolites enterolactone (ENL) and enterodiol (END) have beneficial effects on breast cancer progression. This review aimed to develop a perspective for further research on this type of cancer in the future by giving some general information about FS and its components and evaluating some studies showing potential effects on breast cancer.