The Vietnamese girls were desperate to bounce back after their 0-1 loss to their Uzbekistan sisters.
It took only four minutes for the Southeast Asian side, who made their FIFA Women's World Cup debut in Australia & New Zealand 2023, to take the lead with captain Huynh Nhu nodding home Nguyen Thi Tuyet Dung's cross.
Another header, this time by a diving Tran Thi Hai Linh, doubled Vietnam's advantage in the 22nd minute.
India rang in the changes at the start of the second half to salvage the game but it was Vietnam who scored again with another header, by substitute Pham Hai Yen, in the 73rd minute.
Sandhiya Ranganathan pulled one back for India in the 80th minute.
The Vietnamese team will face the strongest of Group C – Japan, who claimed the Women’s Football Gold Medal at Hangzhou Asian Games, in the last match of the AFC Women’s Olympic Qualifiers second round on November 1.