Abstract Background Various breast cancer (BC) treatments, such as chemotherapy and targeted therapies, increase cardiotoxicity-risk and lead to premature ischemic heart disease and heart failure among survivors. Reducing this adverse risk through early recognition and (preventive) treatment is therefore important. Conversely, we feel that screening for cardiotoxicity is currently insufficiently standardized in daily practice. A fundamental first step in identifying areas of improvement is providing an overview of current practice. Objective This study aims to describe current cardiac surveillance for women with BC during and after cardiotoxic cancer treatment, using routinely collected hospital data in the Netherlands. The study also describes hospital variation in cardiac surveillance. Methods This observational study was performed on claims data provided by Statistics Netherlands. From the data, newly diagnosed BC patients in 2013 ( N = 16,040) were selected and followed up until 2015. Healthcare utilization analyses were performed for all cardiac and oncologic healthcare activities but with a specific focus on cardiac surveillance healthcare activities. In addition, differences between types and individual hospitals were evaluated. Results Almost one third of all BC patients received high risk cardiotoxic treatments ( N = 5157), but cardiac surveillance was rarely performed. Cardiac care provided to patients mainly consisted of ECGs (52.0%) and MUGA scans (26.5%). Cardiac MRI was performed in 0.7% of the patients, echocardiography in 17.7%, and measurement of Troponin and NT-proBNP in 5.1 and 5.8%, respectively. Moreover, we observed a substantial variation in cardiac surveillance between different hospital types and between individual hospitals. Conclusion This study shows that women treated for BC with cardiotoxic treatments do not receive recommended cardiac surveillance. Standardized approaches in clinical care are lacking, resulting in low rates of diagnostic testing and a substantial variation in ...