Single plant cells have hundreds of mitochondria that move around and change their shape through the processes of fission and fusion. The Arabidopsis genome has genes for two dynamin-related proteins, DRP3A and DRP3B, that are similar to genes involved in mitochondrial fission in yeasts. DRP3A and DRP3B were localized to mitochondrial constricted sites and ends. Over-expression of DRP3A or DRP3B with point mutations caused severe elongation of mitochondria. These results show that DRP3A and DRP3B are functional homologues of the dynamin-related protein for mitochondrial fission in yeasts. On the other hand, Arabidopsis appears to have no genes similar to those involved in yeast mitochondrial fusion. Little has been written about mitochondrial fusion in plants. Using a novel photoconvertible fluorescent protein, we have recently shown that mitochondria in live plant cells rapidly undergo fusion and fission on a time scale of seconds. In this mini-review, we focus on plant mitochondrial fission and fusion, and compare them with mitochondrial fission and fusion in yeasts and animals, about which much has been learned in recent years.