The composition and quality of nesting materials may influence the breeding success of cavity-nesting vertebrates, providing protection and optimal temperature to eggs and chicks. Between 2010 and 2013, we studied the composition and preferences regarding nest materials used by cavity-nesters in Andean temperate forests, southern Chile. We deployed 240 nest-boxes, obtaining data for 290 nests for three bird species (Aphrastura spinicauda, Troglodytes aedon and Tachycineta meyeni) and four mammals (Dromiciops gliroides, Rattus rattus, Oligoryzomys longicaudatus and Irenomys tarsalis). Aphrastura spinicauda (n = 170) and D. gliroides (n = 91) comprised 90 % of the nests. A. spinicauda nests were composed mainly of vine tendrils (44.2 %) and branches of trees and shrubs (25.7 %). Dromiciops gliroides used mostly leaves of trees and shrubs (72.9 %), and bryophytes (20.2 %). The predominant and preferred leaf in the nests of both species was from bamboo Chusquea species. Aphrastura spinicauda avoided the leaves of Lophozonia obliqua, whereas D. gliroides avoided vines. These results suggest a previously unknown role of Chusquea spp. in the breeding ecology of cavity-nesting forest vertebrates. The thick matted nests and the acidic pH of the Chusquea spp. leaves may provide protection from predators and have a biocidal effect on pathogens. Chusquea spp. may have an important inluence on the breeding success of cavity-nesters, although the benefits of using this nest material need to be confirmed.