PURPOSE: Women diagnosed with ductal carcinoma in situ (DCIS) of the breast are at greater risk of dying from cardiovascular disease and other causes than from breast cancer, yet associations between health-related behaviors and mortality outcomes after DCIS have not been well studied. METHODS: We examined the association of body mass index, physical activity, alcohol consumption, and smoking with mortality among 1925 women with DCIS in the Wisconsin In Situ Cohort study. Behaviors were self-reported through baseline interviews and up to three follow-up questionnaires. Cox proportional hazards regression was used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for mortality after DCIS, with adjustment for patient sociodemographic, comorbidity, and treatment factors. RESULTS: Over a mean of 6.7 years of follow-up, 196 deaths occurred. All-cause mortality was elevated among women who were current smokers 1 year prior to diagnosis (HR = 2.17 [95% CI 1.48, 3.18] vs. never smokers) and reduced among women with greater physical activity levels prior to diagnosis (HR = 0.55 [95% CI: 0.35, 0.87] for ≥5 h per week vs. no activity). Moderate levels of post-diagnosis physical activity were associated with reduced all-cause mortality (HR = 0.31 [95% CI 0.14, 0.68] for 2-5 h per week vs. no activity). Cancer-specific mortality was elevated among smokers and cardiovascular disease mortality decreased with increasing physical activity levels. CONCLUSIONS: There are numerous associations between health-related behaviors and mortality outcomes after a DCIS diagnosis. IMPLICATIONS FOR CANCER SURVIVORS: Women diagnosed with DCIS should be aware that their health-related behaviors are associated with mortality outcomes.