Ferrochelatase (FECH) is an essential enzyme for the final step of heme biosynthesis. In green plants, its activity has been reported in both plastids and mitochondria. However, the precise subcellular localization of FECH remains uncertain. In this study, we analyzed the localization of FECH in the unicellular red alga, Cyanidioschyzon merolae. Immunoblot and enzyme activity analyses of subcellular fractions localized little FECH in the plastid. In addition, immunofluorescence microscopy identified that both intrinsic and hemagglutinin (HA)-tagged FECH are localized in the mitochondrion. We therefore conclude that FECH is localized in the mitochondrion in C. merolae. © 2013 The Author.