The Vietnamese men's jumped 11 places to 23rd while the women fell nine positions to 16th after round eight of the World Chess Olympiad in Istanbul Thursday.
In the eighth round, the men clashed with host Turkey's strongest team (Turkey has three teams at the event) and beat them 3-1.
Vietnam's top player Le Quang Liem (elo rating 2693) defeated Solak Dragan (2599), while Nguyen Ngoc Truong Son (2639) beat Esen Baris (2587).
Nguyen Van Huy and Nguyen Duc Hoa drew Yilmaz Mustafa and Can Emre.
In the women's contest, after two consecutive wins over the US and the Czech Republic, the Vietnamese women lost 1.5-2.5 to India.
Nguyen Thi Mai Hung (2212) beat Karavade Eesha Sanjay (2371) while Pham Le Thao Nguyen (2393) managed a draw with Dronavalli Harika (2503).
But Le Kieu Thien Kim (2226) lost to Tania Sachdev (2397) and Pham Bich Ngoc (2172) lost to Mary Ann Gomes (2396).
The men, who are now in 23rd place out of the 150 teams in the contest, will next play Britain, while the 16th placed women will clash with Germany.
The tournament ends on Monday.