Abstract: Mitochondrial dynamics are driven by the inner mitochondrial membrane potential, and have significant implications in cell function. Fission and fusion are well established characteristics of mitochondrial dynamics in most cell types. These movements are believed to be geared toward optimizing energy delivery to metabolic sites within the cell. In cardiac cells, mitochondria dynamics and their implications in cell function are poorly studied. The canonical role of mitochondria in ATP production suggests a more involved role for cardiac mitochondria dynamics into regulation of cellular function. In this study, mitochondria dynamics in adult rat, and neonatal, cardiac myocytes, are investigated. The functionality of proteins involved in the fusion and fission of mitochondria are assayed, using recently developed mitochondria targetted tools. We show that while adult cardiac myocytes exhibit relatively dormant mitochondria dynamics, mitochondria in neonatal hearts exhibit dynamics that are comparable to that of primary cell types, albeit more organized. Finally, we investigate the effects of the regulation of expression levels of mitochondrial fission and fusion proteins on calcium signaling in both cardiac cell types.