Breast cancer (BC) in young women, generally defined in oncology as women who are 40 years of age or younger, represents 2 out of 10 BC cases in developing countries. Several research studies, including genetic cancer panel tests, genome-wide association studies, expression analyses and polymorphisms reports, have found that young women with BC exhibit a higher genetic susceptibility and specific genomic signature compared to postmenopausal women with BC. Thus, international guidelines recommend genetic counseling for this age population. This review presents the current state of the art of genetics and genomics with regards to young women with BC.