A survey on the cyanobacterial biodiversity of 7 mangrove environments viz. Vallikunnu, Kadalundi, Kallayi, Mangalavanam, Kumbalam, Kumarakom and Mekkara mangroves of Kerala was undertaken during 2014-2016. In total, 31 species of cyanobacteria coming under 10 genera and 4 families were recorded in all mangrove environments. Maximum species (13 species) of cyanobacteria were recorded from Kadalundi, whereas the minimum was recorded from Mangalavanam (2 species). The genus Oscillatoria was observed with maximum distribution (13 species), followed by Nostoc (5 species) and Lyngbya (3 species). The genus Aphanocapsa, Microcoleus and Scytonema (2 species each) and Chroococcus, Aphanothece, Merismopedia, and Phormidium (1 species each) shows equal distribution. As many as three species, namely Oscillatoria salina, Oscillatoria ornata and Oscillatoria vizagapatensis were common in all mangrove environments except Mangalavanam and Mekkara.