The first flight is scheduled to take off on October 6 and there would be four weekly flights, the carrier said on its website.
Tickets are on sale at 253,000 won (US$188.55) for one-way fare.
The carrier is also planning to start a Seoul-Hanoi service early next year.
South Korea has sent the highest number of visitors to Vietnam since the latter reopened its borders.
In the first seven months of this year Vietnam received 196,000 South Korean tourists, or 20 percent of all foreign arrivals.