The Camili Biosphere Reserve, which is located in the Caucasus Biodiversity Hotspot, is the only biosphere reserve in Turkey. This study aims to determine the mayfly species in this biosphere reserve and to make new contributions to the distribution of Caucasian species. Larval specimens belonging to four families, eight genera, 23 taxa, and 17 species were sampled within 23 sites. Three of these species, namely Ecdyonurus (Helvetoraeticus) adjaricus Kluge, Godunko and Apanaskevich, 2013, Rhithrogena decolorata Sinitshenkova, 1973, and Electrogena squamata (Braasch, 1978) are new records for Turkey, which increased the total number of mayfly species in Turkey to 165. The most distinctive morphological characteristics of the newly added species were given. Besides, information on habitat properties for these species was also provided. Accordingly, all of these three species mainly inhabited the epirhithron section of the streams. They were found in middle- and small-sized streams, preferring stony substrates with moderate to fast current velocity. The study indicates that the number of mayfly species in Turkey is expected to be higher, especially in the North-Eastern Part of the country.