The win came amid heavy snowfall in the French Alps but didn't prevent Hirscher from overtaking Italy's Stefano Gross, who had clocked the fastest time in the first run.
Hirscher clinches slalom win in Val d'Isere
It was also his 14th World Cup podium in Val D'Isere, a new record for a male skier at a single ski resort.
The Austrian is second in the overall World Cup standings with 274 points, behind Henrik Kristoffersen of Norway on 285. They also sit in the same positions in the slalom World Cup standings.
"The second run went much better than the first run," said Hirscher. "I made some mistakes in the first and wasn't skiing smoothly - it wasn't a smooth run.
"For me personally it is cool (to have 274 points). It's good to have great results already in my pocket and it's a big challenge for me to deal with this new situation."
Henrik Kristoffersen of Norway takes 2nd place, Marcel Hirscher of Austria takes 1st place, Andre Myhrer of Sweden takes 3rd place during the Audi FIS Alpine Ski World Cup Men's Slalom on December 10, 2017 in Val-d'Isere, France. g
Image credit: Getty Images
Kristoffersen, who won the two previous editions in the slalom of Val d'Isère, was placed fifth after the first run but moved up to second to claim a 24th podium in slalom.
Sweden's André Myhrer took third place and 60 World Cup points whilst Austria's Michael Matt took fourth with Great Britain's Dave Ryding 19th fastest.