The paper reports the occurrence of 404 species of microlichens belonging to 105 genera and 39 families known so far, from the state of Arunachal Pradesh, a part of the Himalaya biodiversity hotspot. Twelve species, namely Arthopyrenia saxicola, Arthothelium subbessale, Diorygma macgregorii, D. pachygraphum, Graphis nuda, G. oligospora, G. paraserpens, G. renschiana, Herpothallon japonicum, Megalospora atrorubricans, Porina tijucana and Rhabdodiscus crassus, are new distributional records for India. Astrothelium meghalayense (Makhija & Patw.) Pushpi Singh & Kr. P. Singh and Astrothelium subnitidiusculum (Makhija & Patw.) Pushpi Singh & Kr. P. Singh are proposed as new combinations and 66 species marked by an asterisk (*) are new distributional records for the state.