Objectives To investigate trends in cardiovascular disease (CVD) risk following breast cancer using national registry data. Methods A nationwide cohort study was conducted, comprising 163 881 women with in situ (7.6%) or invasive (92.4%) breast cancer and women of the general population, ranging from 3 661 141 in 1996 to 4 566 573 in 2010. CVD mortality rate in women with and without breast cancer and hospitalisation rate after breast cancer were calculated for the years 1996–2010. Age-adjusted CVD and breast cancer mortality within 5 years after breast cancer admission (1997–2010) were compared with 1996 calculated with a Cox proportional hazard analysis. Results The absolute 10-year CVD mortality risk following breast cancer decreased from 56 per 1000 women in 1996 to 41 in 2005 (relative reduction=27.8%). In the general population, this decreased from 73 per 1000 women in 1996 to 55 in 2005 (–23.9%). The absolute risk of CVD hospitalisation within 1 year following breast cancer increased from 54 per 1000 women in 1996 to 67 in 2009 (+23.6%), which was largely explained by an increase in hospitalisation for hypertension, pulmonary embolism, rheumatoid heart/valve disease and heart failure. The 5-year CVD mortality risk was 42% lower (HR 0.58, 95% CI=0.48 to 0.70) for women admitted for breast cancer in 2010 compared with 1996. Conclusions CVD mortality risk decreased in women with breast cancer and in women of the general population, with women with breast cancer having a lower risk of CVD mortality. By contrast, there was an increase in hospitalisation for CVD in women with breast cancer.