The two will face off in the semi-finals of the Southeast Asian qualifying tournament in Jakarta from where the top three teams will qualify.
Indonesia and Malaysia will play the other semi-final with the losers going into a play-off for third place.
Viet Nam have played Australia just once before in futsal, in a semi-final match at the ASEAN Football Federation Futsal Championships in Bangkok in 2007, losing 4-1.
Viet Nam was forced to play powerhouse Australia after allowing Malaysia to claw back in their last group match and draw 2-2 after leading 2-0. Malaysia topped the group on goal difference.
Viet Nam had easily thrashed Cambodia 12-1 and the Philippines 4-1 in other group matches.
The finals will be held in Tashkent, the Uzbek capital, from May 23 to 30.
Thirteen teams have already qualified – hosts Uzbekistan, defending champions Iran, runners-up Thailand, third-placed Japan, China, South Korea, Chinese Taipei, Kyrgystan, Tajikistan, Turkmenistan, Lebanon, Iraq, and Kuwait.