The 12-kilogram primate was found at Laguna Lang Co Resort in Phu Loc in good health condition.
The park's staff will keep a close watch on its movements and ability to integrate into red-shanked douc herds.
The red-shanked douc is the queen of primates, and has been listed as critically endangered in Vietnam’s Red Book.
Spanning 37,500 hectares and covered by evergreen tropical and subtropical rainforests, the Bach Ma National Park affords red-shanked doucs the ideal habitat to develop. It is now home to six herds of red-shanked doucs.
Researchers said the park harbors over 1,700 animal species, accounting for 7 percent of all species currently in Vietnam. A total 69 species are named in the Red List of Threatened Species, including dholes, leopards and saola. Fifteen species are endemic to Vietnam, mostly birds.
Last May, another red-shanked douc weighing 6.3 kilogrammes discovered near Ta Trach reservoir in Huong Thuy town was also released into the park.
