Porthidium nasutum is a pit viper species native to southern Mexico, Central America and northern South America. No subspecies are recognized as being valid.
Adults of Porthidium nasutum are usually less than in total length (tail included), and rarely more than . Females are considerably larger than males. Both sexes are moderately stout.
Porthidium nasutum is found in southern Mexico southward through Central America to western Colombia and northwestern Ecuador in South America. Inhabits the Atlantic lowlands from Mexico (Tabasco and Chiapas) through Belize, Guatemala, Honduras, Nicaragua and Costa Rica to eastern Panama and northwestern Colombia. In the Pacific lowlands, it occurs in southwestern Costa Rica, central and eastern Panama, continuing on to northwestern Ecuador. The type locality given is "Pansos [Panzós], sur les bords du Polochic [Alta Verapaz] (Guatémala)".
The preferred natural habitat of Porthidium nasutum is mesic lowland broadleaf or rainforest from sea level to elevations of about .
Porthidium nasutum is terrestrial.
Porthidium nasutum is ovoviviparous.
The species Porthidium nasutum is classified as Least Concern (LC) on the IUCN Red List of Threatened Species. It is a widespread and moderately common species that is not facing major threats.