Growing evidence suggests that physical activity may be an important part of survivorship care for women with a history of breast cancer. Observational evidence suggests that women who are physically active after breast cancer diagnosis have a 30% to 50% lower risk of breast cancer recurrence, breast cancer death, and overall death compared with sedentary individuals. Although randomized controlled trials have not been performed to test the ability of exercise to improve outcomes in women with early-stage breast cancer, many small intervention studies have shown the safety and potential benefits of exercise in the adjuvant and posttreatment settings. These studies have shown that physical activity can be performed safely both during and after adjuvant treatment for breast cancer, and that women who increase physical activity in these settings experience improvements in fitness, strength, quality of life, and other end points. Although more research is needed to fully define the role of exercise in breast cancer survivors, the many proven benefits of physical activity have led the American Cancer Society and American College of Sports Medicine to encourage regular participation in moderate-intensity recreational activity for most breast cancer survivors. This article reviews the growing evidence that exercise could be an important part of breast cancer survivorship, and describes current exercise guidelines for breast cancer survivors.