Little research examines whether adiposity or post-diagnosis weight changes influence Cardiovascular disease (CVD) among breast cancer patients for whom effects may differ due to treatment and recovery. We studied Stage I-III breast cancer survivors 18 to <80 years, without pre-existing CVD, diagnosed from 1997 to 2013 at Kaiser Permanente. Women reported weight at diagnosis and weight and waist circumference (WC) around 24 months post diagnosis. Using Cox models for time to incident coronary artery disease, heart failure, valve abnormality, arrhythmia, stroke, or CVD death, we examined at-diagnosis body mass index (BMI, n = 3109) and post-diagnosis WC (n = 1898) and weight change (n = 1903, stable, ±5 to <10-lbs or ±≥10-lbs). Mean (SD) age was 57 (11) years, and BMI was 28 (6) kg-m2. Post diagnosis, 25% of women gained and 14% lost ≥10-lbs; mean (SD) WC was 90 (15) cm. Over a median of 8.28 years, 915 women developed CVD. BMI 25-30-kg/m2 (vs. BMI < 25-kg/m2) was not associated with CVD, while BMI ≥ 35-kg/m2 increased risk by 33% (HR: 1.33; 95%CI 1.08-1.65), independent of lifestyle and tumor/treatment factors. The increased risk at BMI ≥ 35-kg/m2 attenuated with adjustment for pre-existing CVD risk factors to HR: 1.20; 95%CI 0.97-1.50. By contrast, even moderate elevations in WC increased risk of CVD, independent of pre-existing risk factors (HR: 1.93; 95%CI 1.31-2.84 comparing ≥100-cm vs. ≤80-cm). Post-diagnosis weight change had no association with CVD. Extreme adiposity and any elevation in WC increased risk of CVD among breast cancer survivors; however, changes in weight in the early post-diagnosis period were not associated with CVD. Survivors with high WC and existing CVD risk factors should be monitored.