Peat bogs play key roles in preserving the stability of ecological relationships, but are some of the fastest disappearing and most endangered ecosystems in Europe. The aims of this study were: (1) to compare the distribution, species richness, diversity, and density of rotifers in microhabitats of a raised bog; and (2) to verify the hypothesis that rotifer density and species composition are dependent on seasonal factors, moss moisture content, and the dominant species of mosses in the microhabitats. Sampling was done monthly from April to November in 2013–2014 in the bog Moszne in eastern Poland (51°27′28.7″ N, 23°07′15.8″ E). The microhabitats sampled included hummocks, slopes, and hollows. A total of 40 rotifer taxa were identified. The highest species richness occurred in the hollows (40), dominated by Sphagnum angustifolium. Markedly lower numbers of taxa were observed on the slopes (28) dominated by Sphagnum magellanicum and Sphagnum rubellum, and in the hummocks dominated by S. magellanicum and Polytrichum sp. During the entire study period all the studied microhabitats were dominated by the Bdelloidea: Habrotrocha angusticollis, Habrotrocha lata, Habrotrocha sp., Dissotrocha macrostyla, Philodina sp. as well as Rotaria rotatoria and Rotaria tardigrada. The greatest species diversity of rotifers was recorded in the hollows (diversity index H′ = 2.307) and the smallest in the hummocks (H′ = 0.769). The density of rotifers was also the highest in the hollows. Statistically significant differences in densities of rotifers between the microhabitats were found (Kruskal–Wallis test: H′(2, n = 33)= 10.33, P = 0.005). The greatest diversity of rotifers and the greatest density were observed in spring