We present the first systematic checklist of medium and large terrestrial mammals on four mountain ranges known as Sky Islands, in northeastern Sonora, Mexico. We used camera traps for recording mammals, with which we documented 25 wild species. Two of the native species are in the IUCN Red List and four are threatened at the national level. We did not document seven wild species with potential distribution at study sites, probably due to limited availability of habitat and/or local extirpation of species. The importance of this work is that we generated an inventory of medium and large mammals in an area considered poorly studied and highly diverse.