 The montane guinea pig is a medium-sized species, growing to a total length of .The colour varies in different parts of the range; in Peru, the dorsal fur is dark reddish-brown mixed with black, and the underparts are dark buffy-grey; in Chile, the dorsal surface is pale agouti brown with paler underparts; in Bolivia, the upper parts are agouti olive and the underparts creamy-white or white.The montane guinea pig is native to the high Andes in South America.