The paper presents water mites (Hydracarina) of peat lands in Bagna Biebrzańskie. 87 species of water mites were collected in the following water habitats: peat ponds, sedges, temporary forest reservoirs, temporary field reservoirs, small permanent water bodies, drainage ditches, ox-bow lakes, and the rivers: Biebrza, Narew, and Wissa. The synecology and distribution of Hydracarina in these habitats were analysed.