Breast cancer (BC) survivors increasingly experience morbidity and mortality due to cardiovascular (CV) events that often result from chemotherapy. Our collaborative experienced investigators utilizing innovative methods implemented within the National Cancer Institute’s Community Oncology Research Program will test whether an individually-tailored physical activity intervention, implemented while participants are receiving chemotherapy, can attenuate physical inactivity, reduce fatigue, and preserve exercise capacity, left ventricular function, and health-related quality of life, all metrics that are associated with or reduce CV risk. By fostering a lifestyle that maintains or increases physical activity and exercise capacity, this project seeks to reduce CV morbidity and mortality among breast cancer patients and thereby improve their overall survival and quality of life.