She finished 0.58sec ahead of Norway's Nina Loeseth and has enjoyed plenty of success at Flachau.
Hansdotter built a healthy advantage on her opening run in Austria, where temperatures plunged close to minus-10 degrees Celsius, and survived a wobble on the second leg to hold off her rivals.
She finished 0.58sec ahead of Norway's Nina Loeseth and has enjoyed plenty of success at Flachau -- winning in 2015 while claiming four other podiums at the resort.
"I made a big mistake on the second run but I was able to regain my speed. It's great to be able to get those feelings back," said Hansdotter, whose last win had come at Lienz in December 2015.
It was a fourth career victory for Hansdotter -- last year's World Cup slalom champion -- although it has been a difficult season for the 31-year-old who had failed to finish on the podium prior to Sunday's third place in Maribor.
Overall World Cup leader Mikaela Shiffrin, who is also top of the slalom standings this term, was in a tie for third place with Switzerland's Wendy Holdener at 0.78sec.
The American increased her lead over defending champion Lara Gut to 365 points after the Swiss straddled a gate on her first run.