The flights will begin on November 21, with five return flights per week.
The expansion means the airline now flies to five Australian cities, after flights to Sydney, Brisbane and Melbourne began earlier this year.
South Australian Tourism Minister Zoe Bettison said she was hopeful the announcement would more Vietnamese tourists headed to Adelaide.
"The Vietnamese economy is going quite strongly and they're keen to travel," she said.
The flights from Ho Chi Minh City take off at 6.35am (GMT+7), land in Perth at 14.20, and after that continue flying to Adelaide and land in Adelaide at 21.10 on Mondays, Tuesdays, Wednesdays, Thursdays and Sundays.
In the opposite direction, the flights depart from Adelaide at 7:25am, land in Perth at 8:55 (local time) and depart from Perth at 9:55 (local time), land in Ho Chi Minh City at 15:40 (local time) on Mondays, Tuesdays, Wednesdays, Thursdays, and Fridays.
The South Australian government hopes the airline will soon announce direct flights to Adelaide without the stopover in Perth.
ABC7 to ask whether the activity was illegal. </p>
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ABC7 contacted Ms Diehl about the photos, but she claimed to have no knowledge only to later say she was "not at liberty to discuss them".</p>
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The photos were soon deleted, but 24 hours later her entire Facebook page disappeared completely. </p>
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Yet other flight attendants and flight crews have come out to show their support for Ms Diehl, saying the controversy had blown out of proportion and the photo was no first-class fault. </p>
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It was not long before colleagues started sharing their own jet engine selfies online with the hashtag #stewsforericka. </p>
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A number of similar images have since been shared, including one with Virigin Airlines owner Richard Branson sitting in the same position which was taken for promotional purposes. </p>
<p></p>"/>Crews fly in to support flight attendant busted over plane engine photo
Francis Wong from the South Australia Vietnamese Business Council said direct flights would mean more tourism into South Australia.
"We say all roads lead to Vietnam in Asia - especially in the ASEAN region - so it's really good to have the direct connections with Vietnam," he said.
VietJet has also announced a further four new international routes to destinations in China, Taiwan, and South Korea.
