Dataset on the epibenthic abundance of Bryozoa on P. crispa and P. oceanica habitats in the NW Mediterranean Sea (Giglio Island, Italy). Samples were obtained via SCUBA diving in summers 2018 and 2019 and analyzed by microscopic determination and counting of specimens. Sampling was part of a larger project on the diversity of the epiphytic invertebrate community on P. crispa mats in the area. The dataset includes details on the sampling efforts, diversity indices (Shannon (H'), Pielou (J')), and density of colonies m-². The numbers of individuals per family were counted on the subsamples. Densities of bryozoa (Dens) were extrapolated using wet weights of the sub- and main sample, as well as the measured surface area of the subsample. Detailed descriptions of the calculations can be found in the corresponding publication (Rossbach et al. (in review)).