Physical activity both before and after breast cancer diagnosis has been associated with improved survival. However, it is not clear whether this association differs by molecular features of the tumor or by recency of the physical activity to the time of diagnosis. We examined the association of prediagnostic physical activity with survival in a cohort of 1,170 women with primary, incident, and histologically confirmed breast cancer, examining tumor molecular subtypes. Cox regression models were used to estimate hazard ratios (HR) and 95 % confidence intervals (95 % CI). Mean follow-up time was 87.4 months after breast cancer diagnosis; there were 170 deaths identified. Compared with inactive patients (<3 h/week), women with higher average lifetime physical activity (>6 h/week) had reduced risk of all-cause mortality (adjusted HR = 0.61, 95 % CI 0.40-0.95; p trend =0.04). There were no clear differences in the associations for lifetime and more recent physical activity. Lifetime physical activity was also weakly associated with decreased risk of breast cancer-specific mortality. Higher lifetime physical activity was associated with reduced risk of all-cause mortality among women with ER-positive tumors (HR = 0.52, 95 % CI 0.29-0.93) and mutant TP53 tumors (HR = 0.22, 95 % CI 0.06-0.72); however, no statistically significant interactions were observed for ER or TP53 status. Our study further supports that prediagnostic physical activity improves overall survival following breast cancer and suggests that the associations of prediagnostic physical activity with survival following breast cancer may vary by molecular features of the tumor, particularly ER and TP53 status.