The paper provides a comparative description of the leech fauna diversity in the Bukhtarma and Shulbinsk water reservoirs, within the Kazakhstan part of Irtysh River. The investigated reservoirs differ from each other in natural and climatic conditions, water regime, as well as level of human impact, which affects the species composition and abundance of leeches. Statistical analysis revealed a 60 % faunal difference in these reservoirs. The total faunal list includes 10 free-living and parasitic species, of which 7 and 9 inhabit the Shulbinsk and the Bukhtarma reservoirs, respectively. These species belong to 2 orders, 3 families and 6 genera. There are four potentially new morphological species (Alboglossiphonia sp., Erpobdella sp., Piscicola sp.1 and Piscicola sp. 2). Besides them, another three species Erpobdella vilnensis, Helobdella stagnalis and Theromyzon tessulatum recorded for the first time in Eastern Kazakhstan.