The Ministry of Culture, Sports and Tourism has ranked Cat Ba archipelago in the north to national heritage status.
The elevation comes as nearby Hai Phong City prepares for next year's National Tourism Year of Song Hong (Red River) Delta.
It will also help the city's plans to submit the area to UNESCO for recognition for world natural heritage ranking.
The archipelago has more than 300 islands, of which Cat Ba is the largest. Limestone mountains surge out of the water in many parts of the area. The archipelago joins the World Heritage protected Ha Long Bay.
The park is home to more than 700 species of flaura and fauna, including rare trees and endangered animals. Its forests remain largely untouched.