A statement from Breast Cancer Now said Miles, who was previously head of major gifts at the housing charity Shelter and head of grants fundraising at the learning disability charity Mencap, had tripled net income at Anthony Nolan during her seven years with the charity.
She will take up the role at Breast Cancer Now, which was formed last year by the merger of Breast Cancer Campaign and Breakthrough Breast Cancer, on 6 June.
She replaces Jen Dougan, who has gone back to being a consultant after three years in the role, first at Breast Cancer Campaign.
In a statement, Miles said it was a time of real opportunity for Breast Cancer Now.
"I’m very much looking forward to working with the exceptional team to take the charity’s fundraising and influencing to the next level," she said. "Breast Cancer Now’s ambition is ultimately to fund the research that will finally stop women dying from breast cancer, and we’ll need everyone’s support to help us get there."
Baroness Delyth Morgan, chief executive of Breast Cancer Now, said Miles would be a "tremendous asset" to the charity.
"We are thrilled to welcome Catherine as our new director of fundraising," said Morgan. "She brings with her a wealth of experience and an impressive track record in developing fundraising at leading UK charities."