Background Osteogenesis imperfecta (OI) is a hereditary connective tissue disease often due to mutations in genes coding for type 1 collagen. Collagen type 1 is important in the development of the heart and vasculature. Little is known about the risk of cardiovascular disease (CVD) in OI. Objective To investigate the risk of symptomatic CVD in OI. Design A Danish nationwide, population-based and register-based longitudinal open cohort study. Participants All patients registered with the diagnosis of OI from 1977 to 2013 and a reference population matched 5:1 to the OI cohort. Measurements Sub-hazard ratios for mitral and aortic valve regurgitation, atrial fibrillation and flutter, heart failure and vascular aneurisms and dissections comparing the OI cohort to the reference population. Results We identified 687 cases with OI (379 women) and included 3435 reference persons (1895 women). The SHR was 6.3 [95% CI: 2.5–15.5] for mitral valve regurgitation, 4.5 [95% CI: 1.4–13.9] for aortic valve regurgitation, 1.7 [95% CI: 1.1–2.8] for atrial fibrillation/flutter, and 2.3 [95% CI: 1.4–3.7] for heart failure. The SHRs were not increased arterial aneurisms or dissections. Limitation Our results were limited by lacking clinical information about phenotype and genotype of the included patients. Conclusion We confirm that patients with OI have an increased risk of CVD compared to the general population. This held true even when adjusting for factors that are known to contribute to development of these diseases. Our results suggest that the collagenopathy seen in OI may be part of the pathogenesis of CVD in OI.