Mitochondria are dynamic organelles that were found to fuse and divide in many different cell types. Mitochondrial fusion plays important roles in maintenance of respiratory capacity, dissipation of metabolic energy, and inheritance of mitochondrial DNA. While the molecular machinery of mitochondrial fusion has been characterized in great detail in yeast and mammals, only little is known about mitochondrial fusion in higher plants and algae. We asked whether mitochondrial fusion can be observed in the unicellular green alga Chlamydomonas reinhardtii. Mitochondria were stained with fluorescent dyes in gametes, and mixing of fluorescent markers was detected by fluorescence microscopy in zygotes indicating fusion. Mitochondrial fusion was observed in wild type zygotes, and also in respiratory mutants, albeit with less efficiency. We conclude that mitochondria readily fuse in green algae.