Bovine leukemia virus (BLV) is the causative agent of enzootic bovine leukemia. It is proposed that BLV is restricted to bovines, but there are some reports of its presence in humans and its possible relationship with breast cancer. Considering that any relation or association between this virus and breast cancer could be relevant to human public health and to cattle producers worldwide, it is crucial that several research groups keep investigating in the topic with the aim of confirming the role that this virus should have in breast cancer development. Due to the lack of a vaccine, prevention and control strategies should be implemented by governments where livestock is rising.