Breast cancer is traditionally viewed as an estrogen-dependent disease in which the androgen receptor is inhibitory, counteracting the oncogenic activity of estrogen receptor-α. Most likely as a result of this cross-talk, the androgen receptor has prognostic value in estrogen receptor positive disease, with androgen receptor positivity reported to correlate with a better prognosis. Activation of the androgen receptor pathway has been previously used as a therapeutic strategy to treat breast cancer, but its usage declined following the introduction of the anti-estrogen tamoxifen. More recently, it has been demonstrated that a sub-set of triple negative breast cancers (molecular apocrine) are dependent upon androgen signalling for growth and therapies that inhibit androgen signalling, currently used for the treatment of prostate cancer e.g. the antiandrogen bicalutamide and the CYP17 inhibitor abiraterone acetate, are undergoing clinical trials to investigate their efficacy in this breast cancer sub-type. This review summarises the current knowledge of androgen receptor activity in breast cancer.