Breast cancer usually grows very quickly, becoming insensitive to blood flow in nearby veins; because of that, inside solid tumors it's possible to find a hypoxic environment, in other words, an environment where oxygen is less available. Another feature of cancer is its angiogenesis rate, because of the high energy demand, new blood vessels must be produced to take nutrients inside the solid tumor mass. Even with normal blood flow bringing the cancer oxygen and nutrients, its cells favor hypoxia, in an event known as Warburg Effect. According to the Warburg Effect, cells, even with normal oxygen rates, prefer to use fermentation instead of the citric acid cycle to produce ATP. For the cancer to operate normally in hypoxia, a transcription factor family is activated, known as hypoxia-induced factors (HIF), composed of a HIF-1β and a HIF-1α subunits. As HIF-1α is expressed during hypoxia, it is a great target for treatments and a breast cancer biomarker. Because of the role of HIF-1α in cancer and the high incidence of breast cancer worlwide, this review was performed in order to bring the most recent results concerning the role HIF-1α can exert in breast cancer development and progression.