The fossil rodents of the late Eocene to early Oligocene Vieja Group are described. They include the paramyids Leptotomus leptodus, L. gigans n. sp., Mytonomys gaitania, Microparamys perjossus n. sp., Ischyrotomus cf, petersoni and Manitsha johanniculi n. sp.; the ischyromyids Ischyromys blacki n. sp, and Titanotheriomys veterior; the cylindrodonts Cylindrodon fontis, Pseudocylindrodon neglectus, P. texanus n. sp., Ardynomys occidentalis, Jaywilsonomyinae n. subf., Jaywilsonomys ojinagaensis and /. pintoensis; the eomyids Adjidaumo cf. minutus, Viejadjidaumo magniscopuli n. gen., n. sp., Aulolithomys bounites, Meliakrouniomys wilsoni and Yoderimys lustrorum n. sp.; the eutypomyid Eutypomys inexpectatus n. sp.; the possible zapodid cf. Simimys sp. indet., and the possible cricetid Subsumus candelariae n. gen., n. sp. Skulls are described for Pseudocylindrodon texanus, Viejadjidaumo magniscopuli and Yoderimys lustrorum, and partial ones for Ischyromys blacki, Titanotheriomys veterior, Jaywilsonomys ojinagaensis, Aulolithomys bounites and Eutypomys inexpectatus. The Vieja fossils help to close the gap between late Eocene and Early Oligocene North American rodent faunules.