Glandulocaudines occur in practically all major South American drainages. Along Pacific drainages, they are distributed from Costa Rica to Ecuador, and along Atlantic drainages, their range extends to northern Argentina. These fishes are found in every South American country, including Trinidad and excluding Chile; they inhabit streams that are tributaries to larger rivers such as the Amazon, Orinoco, and Paraguay Rivers in tropical species, or coastal streams tributary to the Atlantic and Pacific Oceans and the Caribbean Sea in the few subtropical species.
The habitats of these fish vary. A few species are known from elevations.