Mitochondria are organelles highly dynamic in most types of cells, constantly changing morphology and forming dynamically continuous networks. Defects of mitochondrial dynamics are associated with various human diseases including neurodegenerative diseases and cardiovascular diseases. In the heart, mitochondria are rigidly organized between myofilaments into a crystal-like lattice pattern, the apparently limited mitochondrial movement raises the question of whether mitochondria communicate with each other dynamically. A large body of evidence reveals abnormal mitochondrial morphology in cardiac diseases and that deficiencies of mitochondrial dynamic related proteins lead to cardiac dysfunctions, indicating an essential role of mitochondrial dynamics in regulating the cardiac function. Here we will review mitochondrial dynamics in the heart with the focus on recent findings of the direct inter-mitochondrial communication in adult cardiomyocytes, and will discuss the possible regulating mechanisms.