The Sierra Bacadéhuachi in east-central Sonora is the westernmost mountain range in the Sierra Madre Occidental (SMO), located east of Bacadéhuachi, Municipio de Bacadéhuachi, 34 km east of the Chihuahua border, and 165 km south of the Arizona border. The vegetation ranges from lowland foothills thornscrub up through desert grassland to oak woodland and pine-oak forest. The flora was sampled in December 1995, July 2008, June, August, and September 2011, and March 2012. The flora totals 442 taxa in 297 genera and 96 families. The most species-rich families and genera are Asteraceae (53 taxa), Fabaceae (48 taxa), Poaceae (46 taxa), Quercus (11 species), Cheilanthes (8 species), Muhlenbergia (7 species), Bouteloua (6 species), and Pinus (5 species). Twenty-two species are non-native (5.0%), 10 of them grasses. No species are endemic. Although tree composition and structure of the upland woodlands and forests are similar to the Yécora, Sonora, area to the south, the preliminary Bacadéhuachi flora is less diverse.