There are currently 192 bryophyte species (156 mosses, 31 liverworts and 5 hornworts) documented from San Luis Obispo County, California. Similar to the vascular flora of the county, the bryophyte flora strongly reflects the transitional nature of the region, which lies near the intersection of the Coast Ranges and Transverse Ranges and supports a large and diverse set of vegetation types. Important floristic and biogeographic patterns include a distinctive suite of species from closed-cone coniferous forests and several noteworthy intrusions of Mojave Desert species into the Coast Ranges. A high proportion of species are known from the county from only one or a few collections, indicating that additional floristic work in the county is very likely to yield new records, with many of these promising to add to the biogeographic significance of the region.