The 45-year-old singer successfully battled the disease in 2003, but learned last winter it had recurred, forcing her to cancel a planned concert tour.
"In light of Breast Cancer Awareness Month l wanted to take the opportunity to support a cause particularly close to my heart," the BBC quoted Anastacia as saying.
"l was diagnosed with breast cancer for the second time earlier this year and am currently in the final stages of recovery after undergoing a double mastectomy," she said. "It has been an intense journey, but l am feeling great and ready to start the next chapter. Breast Cancer Awareness Month gives all who are facing this disease a chance to gain strength and support from each other. Early detection has saved my life twice. I will continue to battle and lend my voice in any way I can."