A census in the Virunga Massif, where most of the world's mountain gorillas live, revealed 480 individuals living in 36 groups, the BBC reported Tuesday.
Thirty years ago only 250 gorillas survived in this same area, conservationists say.
Three contiguous national parks are found within the Virunga Massif: Parc National des Virunga in the Democratic Republic of Congo, Volcanoes National Park in Rwanda and Mgahinga Gorilla National Park in Uganda.
Conservationists credit the increase in gorilla numbers to collaborative "transboundary" efforts by organizations in the three countries.
However, the African Wildlife Foundation and International Gorilla Conservation Program say the animals are still very much under threat.
A recent five-day patrol in the Virunga Massif discovered and destroyed 200 poachers' snares, the two organizations said in a joint statement.
While poachers usually do not directly target the gorillas, the snares they set for other animals are still a threat, the statement said.
"Collectively, we cannot let down our guard on the conservation of these incredible animals," Eugene Rutagarama, director of the IGCP, said.
"While mountain gorillas are physically strong, they are also incredibly vulnerable."