The win marks a good start for the team in Group B, which includes Iran , Turkmenistan , Bahrain and Vietnam.
At the opening game in Qatar Asian Games four years ago, Vietnam lost 2-1 to Bahrain .
Midfielder Nguyen Thanh Trung put Vietnam ahead just 34 minutesinto the game when he slotted home Pham Thanh Luong's through-ball.
Vietnam focused on a counter-attacking game, to nullify thesuperior height and strength of their Bahraini opponents, and took thelead into half time.
Fifteen minutes into second half,Trung nearly scored a second goal but his free kick was saved byBahrain 's keeper Mushaima.
In the 72nd minute, NguyenTrong Hoang made it 2-0 from a quick counter-attack, before strikerNguyen Anh Duc scored the third goal in the 88th minute.
Bahrain pulled back a consolation goal in the last minute.
Vietnam will meet Turkmenistan on Nov. 10 and Iran on Nov 13 at the Guangdong People's Stadium.
Team assistant coach Phan Thanh Hung said the team would try their bestto take a second or the best placed third in the group, which set them aberth in the knock-out round.
Twenty-four teams aretaking part in the under-23s tournament, with the top two and four ofthe best third-placed sides from the six groups advancing to the roundof 16./.