Hirscher won his third consecutive slalom with a 0.29-second won over Andre Myhrer of Sweden.
"It is really a tough hill, but it is always amazing to ski here in Adelboden," said Hirscher, who leads Norway's Aksel Lund Svindal by 23 points in the overall standings.
Warm weather deteriorated the conditions on the race course, but Hirscher turned in a combined two-run time of 1 minute, 49.75 seconds. Myhrer, one of three Swedes among the top 10 finishers, was timed at 1:50.04.
Norwegian teenager Henrik Kristofferson took third place with a 1:50.41.
Germany's Felix Neureuther, who won Saturday's giant slalom at Adelboden, and American Ted Ligety were among the competitors who failed to finish the race.
David Chodounsky was the top U.S. finisher with an eighth-place time of 1:51.45. "Anytime you get points, it's a good day," he said. "It was tough and it was fast on the steepest pitch on the tour."