The heart contains not only cardiomyocytes but also other cell types such as endothelial cells and fibroblasts. Functional crosstalk among these cell types is important for normal cardiac function and is also involved in disease pathophysiology. Recent data indicate that redox signalling within and between endothelial cells and cardiomyocytes, both through direct and indirect mechanisms, is an important aspect of the functional communication between these cell types. Such signalling influences contractile function, cardiomyocyte growth, hypertrophy, angiogenesis, and fibrosis, and may play an important role in cardiac remodelling in disease.