Chiasmocleis mantiqueira is a small microhylid frog recently described from an Atlantic rain forest fragment found in the state of Minas Gerais, southeastern Brazil, whose biology is poorly know. Here, the tadpole and the vocalizations of this species are described from the type locality, along with some information about its natural history. Characteristics of larval external morphology of C. mantiqueira are similar to other described tadpoles of the genus: oral disc without keratinized mouthparts, spiracle single, posterior ventral, and medial vent tube. The body is depressed, rectangular in dorsal view and oval in lateral view, and the tail has a flagellum. The species exhibits an explosive breeding behavior, like other Neotropical microhylids. However, unlike other species in this genus, males of C. mantiqueira do not have a vocal sac, and its call is composed of a single harmonic, not a pulsed, note. Thus, the characteristics of the call of C. mantiqueira contradict the hypothesis that call structure can support the monophyly of Chiasmocleis, and further data are required to clarify the relationship of the species in this genus.