K9HeartCircDB is a publicly accessible database of circular RNAs (circRNAs) derived from canine left ventricular tissues in a tachypacing-induced model of non-genetic dilated cardiomyopathy. It enables researchers to explore circRNA features, including divergent primers, siRNAs, predicted miRNA binding sites, and novel polypeptides encoded by circRNAs. The platform serves as a translational resource for studying circRNA-mediated mechanisms in cardiac remodeling and heart failure.