Cardiac fibroblasts produce the extracellular matrix (ECM) scaffold within which the various cellular components of the heart are organized. As well as providing structural support, it is becoming evident that the quality and quantity of ECM is a key factor for determining cardiac cell behavior during development and in pathological contexts such as heart failure involving fibrosis. Cardiac fibroblasts have long remained a poorly characterized cardiac lineage. Well characterized markers are now paving the way for a better understanding of the roles of these cells in various developmental and disease contexts. Notably, the relevance of processes including endothelial-tomesenchymal transition and the recruitment of circulating fibroblast progenitors in heart failure has been challenged. This review describes the latest findings on cardiac fibroblast markers and developmental origins, and discusses their importance in myocardial remodeling. Effective modulation of cardiac fibroblast activity would likely contribute to successful treatment of various cardiac disorders.