It is endemic to south-eastern Brazil where it occurs in the Serra do Mar and Serra da Mantiqueira ranges in the states of Rio de Janeiro, São Paulo, and Minas Gerais.

[1][2][3] However, Araujo-Vieira and colleagues suggests that the Serra da Mantiqueira population could represent Sphaenorhynchus canga; the two species are similar.

In 1981 John D.Lynch designated a neotype for the species, erroneously believing that the holotype (the only known specimen, in the collections of the Institut für Zoologie der Universität Wien) was lost.

However, the neotype specimen was not a hylid but a centrolenid, later described as a distinct species, Centrolenella savagei (now synonym of Ikakogi tayrona[5]).

[7] Sphaenorhynchus platycephalus lives on vegetation above large ponds or lakes or at the edge of forests.