The striking black-and-yellow snake measures 60 cm (2.1 ft) and has horn-like scales above its eyes.
The newly discovered snake, named Matilda's horned viper, has been described in the journal Zootaxa.
The exact location of the new species is being kept a secret, because it could be of interest to the illegal pet trade.
Campaign group the Wildlife Conservation Society said the snake's habitat, estimated at only a several square km, is already severely degraded from logging and charcoal manufacture.
The authors of the study in Zootaxa expect the viper will be classified as a critically endangered species.
They have already established a small captive breeding colony.