BACKGROUND: In breast cancer patients, coincidental detection of CAC at chest CT may be important in determining cardiovascular (CV) outcomes and facilitate CV disease primary prevention strategies. METHODS: 408 consecutive breast cancer patients referred to cardiac oncology clinic were included in the study. 256 patients without a prior history of coronary artery disease had undergone a chest CT. CT images were reviewed to detect CAC. Framingham risk score (FRS) was calculated and patient electronic medical records were interrogated to document the incidence of a composite clinical end point of all-cause mortality and cardiac events (coronary revascularization, heart failure hospitalization and de novo atrial fibrillation). Prevalence of statin prescribing was also collected. RESULTS: Patients were followed for a median of 6.5 years. 112 clinical events occurred. Clinical follow up was 98%. CAC was found in 26% of patients. On multivariable analysis, CAC and advance cancer stage, but not FRS predicted the composite clinical end point (OR for CAC 2.59, p < 0.01). CAC but not FRS also predicted the incidence of cardiac events (OR for CAC 4.90, p < 0.01). CAC was present in 7.3% of patients with low FRS; none had been prescribed a statin. In patients with CAC and FRS ≥ 10%, 45% were not on a statin. CONCLUSION: CAC is a common coincidental finding at CT chest in breast cancer patients referred to cardiac oncology. CAC but not FRS was predictive of composite clinical events and cardiac events. Detection of CAC at chest CT could alter the prescribing of primary prevention strategies to help prevent future cardiac events in breast cancer patients.