Until now researchers have been unable to photograph the monkey, Rhinopithecus strykeri, whose distinctive upturned nostrils are said to make it sneeze in the rain.
The species was discovered in October 2010 and it was believed that the species was isolated to the Kachin state of northeastern Myanmar.
Researchers writing in the American Journal of Primatology say the discovery reveals the international range of this critically endangered species.
An expedition of scientists from the Nature Conservancy China Program travelled to the Yunnan province of China after a forest ranger took photos of a group of snub-nosed monkeys in a forest in near Pianma, in Yunann's Lushui County.
"The population of this species is hard to estimate, but based on our contacts with the monkey group both in October 2011 and in March 2012 we estimate the population to be less than 100 individuals," expedition leader Yongcheng Long said.
"However, while we now know the home range to be far greater than previously believed, we still do not yet know the true population number or the extent of their home range as the monkeys are shy and very hard to access."
Local hunters claim the monkey is easy to find when it is raining because they often get rainwater in their upturned noses causing them to sneeze, something scientists say they've not observed.