The pine-oak forests of Mexico are reservoirs of high biological diversity, largely due to their high richness of vascular flora. However, mosses have received little attention. We studied the floristic composition, diversity, and species richness of the moss community in the pine-oak forests of the Sierra Norte of Oaxaca, Mexico. A comprehensive list of the species occurring in the region was made by reviewing herbarium databases and conducting fieldwork. We analyzed alpha and beta diversity, as well as community structure, based on 60 sampling sites. Our results show the occurrence of 339 species of mosses in the study area, distributed in 168 genera and 52 families. We found high α and β diversity values compared with other vegetation types in Mexico. Our study provides a more detailed portrait of the high moss diversity occurring in the region.