The flagpole, located on Khoang La San Mountain at an elevation of 1,459 metres, is about 1.4 km from the point where Vietnam, Laos and China meet.
Provincial authorities said the designation would support sustainable tourism development while preserving the area's historical and cultural significance.
Dien Bien province last year upgraded an 8-km access road to the site as part of a VND 40 billion (USD 1.5 million) project aimed at improving border infrastructure and boosting tourism.
Standing 45.19 metres tall, the flagpole has become a popular destination for visitors to Vietnam's westernmost region and a symbol of the country's border sovereignty.
