Mitochondria are dynamic organelles and maintain their structure through two opposing processes of fusion and fission. In mammals, there are many factors which influence the equilibrium between mitochondrial fusion and fission. It has been known that mitochondrial fusion is controlled by mitochondria-shaping proteins, including the large GTPase mitofusins (Mfn1/2) and optic atrophy protein 1 (OPA1), whereas the protein Fis1 and dynamin-related protein 1 (Drp1) are the key mediators of mitochondrial fission. Recent data revealed the relationship between mitochondrial fusion/fission and Ca2+ signaling. Ca2+ handling is controlled by the change of mitochondrial fission-fusion balance. On the other hand, intra- and near-mitochondrial Ca2+ signals can modify mitochondrial morphology and cellular distribution.