Catecholamines, canonically associated with the sympathetic nerves and the adrenal medulla, are also produced by neuroparacrine cells within the heart. Despite their putative importance, the precise functions of these neuroparacrine cells in the heart are not well understood and their clinical implications remain to be defined. In this review, we first explore the historical context and recent advances in research on intrinsic cardiac adrenergic (ICA) cells, focusing on their unique characteristics, distributions, and progenitor-like potential during cardiac development. We then examine their contributions to both physiological and pathological cardiac states. We further discuss a recently identified population of catecholaminergic cardiomyocytes; we discuss their involvement in cardiac development, maturation, and their potential interaction with sympathetic innervation during development. By reviewing these findings, we provide new insights into the endogenous production of catecholamines within the heart and its relevance to cardiac development, physiology and disease, and its potential clinical implications.