It was on the Italian course last February that Northug claimed gold in the 15km freestyle at the 2013 World Championships.
And 11 months on the 27-year-old was at it again as he came home first in the 10km classic, finishing in 24:45.6 minutes for gold.
Northug was 9.7 seconds ahead of compatriot Martin Johnsrud Sundby as Norway dominated the event with Chris Jespersen completing the podium in third and Sjur Roethe finishing fourth.
Despite coming off second best in Val di Fiemme there was still plenty to celebrate for Sundby as he clinched the Tour de Ski sprint standings.
And with just one event remaining Sundby also retained his lead in the overall Tour de Ski standings as he is 48.5 seconds ahead of Northug ahead of Sunday’s finale.
Sundby also leads the overall World Cup standings on 585 points, with Jespersen second and Russian Alexander Legkov third.