It is found in the Pacific lowlands of El Salvador, Guatemala, and southeastern Mexico (eastern Oaxaca, Chiapas).

[1][2] The specific name robertmertensi honors Robert Mertens, a German zoologist and herpetologist.

The fingers are short and broad, slightly webbed, and have small discs.

[4] Dendropsophus robertmertensi inhabit sub-humid and humid lowlands and foothills at elevations up to 700 m (2,300 ft) above sea level.

Breeding takes place in small temporary and permanent ponds.