Recreational physical activity (RPA) is associated with a reduced risk of developing breast cancer, but there is limited research on whether prediagnostic RPA influences survival after breast cancer diagnosis or not. We evaluated the association between prediagnostic RPA and risk of death in 1508 women with a first breast cancer diagnosis during 1996 and 1997 in the population-based Long Island Breast Cancer Study Project. A 5-year mortality, through the end of 2002, was assessed using the National Death Index (N=196). An in-person interview was completed shortly after diagnosis to obtain information on lifetime RPA, which was expressed as metabolic equivalent task hours per week (MET-h/week). A lower risk of all-cause death was observed for women who engaged in an average of 9 or more MET-h/week of RPA from menarche to diagnosis compared with women who did not exercise [age-adjusted and BMI adjusted hazard ratio (HR)=0.57; 95% confidence interval (CI)=0.39–0.83], an association that was similar when evaluated according to menopausal status. Compared with women who did not engage in moderate RPA, those who engaged in any moderate intensity lifetime RPA (>0 MET-h/week) were found to have lower all-cause mortality (HR=0.62; 95% CI=0.46–0.84) and breast cancer-specific mortality (HR=0.64; 95% CI=0.43–0.93). Among postmenopausal women, RPA that took place after menopause resulted in a decrease in overall mortality, whereas no association was observed for RPA which took place prior to menopause (for >0 MET-h/week of RPA vs. no RPA, the HR=0.61; 95% CI=0.39–0.94 and HR=1.00; 95% CI=0.65–1.54, respectively). This study provides support that RPA prior to breast cancer diagnosis improves survival.