This paper summarizes a first account of the bat fauna in the middle elevations of the Tambito Nature Reserve in the Colombian Chocó. A month-long survey using mist netting found 13 genera comprising at least 26 species. As expected from mist net bias, virtually all the bats captured were understory phyllostomids, with few exceptions. Nonetheless, high ecological diversity was confirmed with frugivorous, nectarivorous, insectivorous and sanguivorous guilds represented. Estimates using extrapolation place the real understory diversity somewhere above 30 species, making this a key site for conservation of bats in general, and the genera Sturnira, Platyrrhinus, and Vampyressa, in particular.