This article presents CARDIO:DE, the first freely available and distributable large German clinical corpus from the cardiovascular domain. It encompasses 500 clinical routine German doctor’s letters from Heidelberg University Hospital that were manually annotated and de-identified. Two high-quality manual annotation layers were added to CARDIO:DE, (1) medication information and (2) CDA-compliant section classes. This corpus offers unique opportunities for collaborative and reproducible research on natural language processing models for German clinical texts.