The animal was photographed by a camera trap operated by a joint team from Fauna & Flora International, Biodiversity and Nature Conservation Association, and People Resources and Conservation Foundation.
The camera, triggered by infrared sensors, was located in the mountains of Burma's northerly Kachin state bordering China, NewScientist.com reported.
"We were very surprised to get these pictures," Saw Soe Aung, a field biologist who set the camera traps, said. "It was exciting to see that some of the females were carrying babies -- a new generation of our rarest primate."
The snub-nosed monkey, Rhinopithecus strykeri, was first described scientifically from a dead specimen collected by a local hunter in 2010.
Conservationists said hunting and habitat loss mean the species will likely be classified as critically endangered by the International Union for Conservation of Nature.
The population of the monkeys is thought to be less than 300 individuals, they said.