The blue green damselfishes were described as a complex of two species (Chromis viridis and Chromis atripectoralis), mainly based on the colouration of the pectoral fin base. In this study, the authors analysed the mitochondrial control region of 88 blue green damselfishes from Indonesia, the Philippines, Red Sea and the Great Barrier Reef. The phylogenetic analysis revealed four major monophyletic clades. Two clades included specimens of C. atripectoralis from the Great Barrier Reef and individuals of C. viridis from the Red Sea, respectively. The remaining individuals of C. viridis from Indonesia and the Philippines were grouped into two clades without phylogeographic structure. The obtained results (1) verified that C. viridis and C. atripectoralis are distinct species and (2) revealed three deep evolutionary lineages of C. viridis in the Indo-Malay Archipelago and the Red Sea.