The animals consist of two civet wild cats, one Macaca arctoides and two Macaca mulatta monkeys in which Macaca arctoides and Macaca mulattas are listed as endangered and rare species.
The animals are said to have adapted well to their return to nature.
Early this month, 17 wild animals were also released into Phong Nha-Ke Bang National Park, including many kinds of rare and endangered species.
So far this year, up to 39 wild animals have been handed over the national park, which has helped to boost the bio-diversification of the park.