BACKGROUND: Physical activity has been related to improved breast cancer outcomes. Especially in the older breast cancer population, physical activity may be important because old age is associated with comorbidities and decreased physical function. The purpose of this study was to investigate the relation between physical activity and overall survival, breast cancer–specific survival, and recurrence in several age groups of postmenopausal breast cancer patients. METHODS: The Tamoxifen Exemestane Adjuvant Multinational Lifestyle study was a side study of the Tamoxifen Exemestane Adjuvant Multinational trial and prospectively investigated lifestyle habits of postmenopausal, hormone receptor–positive breast cancer patients. The relations between prediagnosis and postdiagnosis physical activity and overall survival, breast cancer–specific survival, and recurrence-free survival were assessed with Cox regression and com-peting risk regression models. RESULTS: Among 521 patients, high levels of physical activity before and after the diagnosis were asso-ciated with better overall survival (the multivariate hazard ratios were 0.50 [95% confidence interval 5 0.26-0.98] and 0.57 (95% confidence interval 5 0.26-1.40] for patients who were very active before and after the diagnosis, respectively, in comparison with inactive patients). This was most evident in patients who were 65 years old or older. Physical activity was not significantly associated with breast cancer–specific survival or the relapse-free period. CONCLUSIONS: Overall survival was better for patients who were active before and after the diagnosis. In contrast with previous studies, breast cancer survival and the risk of recurrence were not sig-nificantly associated with physical activity. These findings confirmed the need for more studies investigating the use of physical activ-ity to supplement breast cancer treatment in older patients.