With a blistering second run, the World Cup holder and leader came back from eighth in the morning leg to win in a combined time of one minute 51.75 seconds.
Beaten in Saturday's giant slalom after a bad mistake on one of the last gates, Hirscher reasserted his supremacy and increased his lead in the World Cup overall standings to 126 points over Norway's Aksel Lund Svindal.
"Obviously, it's not the same outcome as yesterday. Sometimes you make the most of the opportunity and sometimes you push too hard," Hirscher told reporters.
"It has nothing to do with pressure as I handle it well when I'm leading after the first run. It's just that today's second run was extraordinary. I've surprised myself," said the Austrian, the first skier to win the Adelboden slalom twice.
Svindal, his main rival for the big globe who does not take part in slaloms, acknowledged the exceptional performance by the Austrian when he wrote on his Twitter account: "Wow, Marcel Hirscher!"
Winner in Madonna di Campiglio, Zagreb and Adelboden as well as finishing on the podium of the two other slaloms held this season, Hirscher is now a comfortable leader in the discipline's World Cup.
Holder Andre Myhrer of Sweden straddled a gate in the second leg for the first time since the same race a year ago.
Veteran Mario Matt, who was in the top three in Zagreb a week ago, finished second, 0.30 seconds adrift.
It was the 33-year-old Austrian's 36th World Cup podium in a slalom.
"There's a mix of generations but I wouldn't say Mario Matt is an old skier, he's just a very good skier you can never rule out", said Hirscher.
Italy's Manfred Moelgg, fastest in the first leg, finished third, 0.62 adrift for his first slalom podium spot in three years.
The men's circuit remains in Switzerland for next week's traditional racing weekend in Wengen.
- Sports & Recreation
- Marcel Hirscher
- Aksel Lund Svindal