Goals to Angus Thurgate and Ben Folami sent the Australians on their way, with Van Nam Le's effort five minutes from full-time ensuring a nervy finish at Patriot Stadium.
The vital three points now moves Ante Milicic's men one step closer to a quarter-final berth ahead of Thursday's (AEDT) crunch Group C clash with Jordan.
Fresh from their frantic draw with Korea Republic, the Young Socceroos came into Monday night's contest looking to assert their dominance from the outset.
While the Vietnamese threatened early on, Thurgate's cool finish towards the end of the first half gave Australia some breathing room.
Hoang Anh Tuan's side stepped up the pressure in the second half but soon fell victim to the ever-impressive Folami, the Ipswich Town striker rifling his effort home with ease.
And while Van Nam gave the Southeast Asians some measure of hope in the 85th minute, the Young Socceroos held on for the deserved victory.