Rio Turvo State Park (RTSP) is a Conservation Unit located within the Atlantic Forest biome in the Vale do Ribeira region of the State of São Paulo, Brazil. Considering the lack of knowledge regarding its bryoflora, we performed a floristic inventory of RTSP (following the random-walk method), the results of which we report here including discussion of the geographical distribution (Brazil and worldwide), substrate colonization, life forms and reproduction of the species. We found a total of 414 species, which represents 30 % of all known bryophyte species in Brazil. Dioicous species were predominant over monoicous species, the most colonized substrate was tree trunk (40 % of all species) and the predominant life form was mat (47 %), indicating that the floristic composition is influenced by the environmental conditions of the area (high humidity, dense vegetation and shading). Although anthropogenic intervention is present in RTSP, it harbors huge biodiverse potential, since 22 % of the species are rare. Furthermore, 16 new occurrences were recorded for the State of São Paulo. The information provided by this study exalts the importance of this Conservation Unit in the preservation of bryophytes, as well as all the biodiversity of its included ecosystems.