[1][2][3] It is endemic to the coastal areas of the Bahia state in eastern Brazil; it is known from the municipalities of Itacaré, Ilhéus, and Una.

There may be irregular dark patches, inter-orbital lines, or a mid-dorsal Y-like pattern.

Calling males were observed from February to September, but greatest activity was from June onward.

[1] Adelophryne mucronatus occurs in shaded areas of primary and disturbed forests at elevations of 79–126 m (259–413 ft) above sea level.

While it also occurs in disturbed forests, it is more abundant and the breeding season is longer in pristine ones.