Paris captured the final race of the campaign in 1:33.07 to edge Fill by .08 of a second with Swiss Carlo Janka third on 1:33.25 and Jansrud a distant 11th in Aspen.
Jansrud led Fill by 33 points in the downhill title chase entering the final race, but with 80 points for his runner-up effort, Fill finished on 454 with the Norwegian ending on 431.
The video below shows some of the highlights of the day for the Italian skiers.
It was the second World Cup downhill crown in a row for Fill, who last year became the first Italian to win the discipline, edging Aksel Lund Svindal by 26 points.
Paris, the first racer down the course, set the mark to beat that held all day and Fill, starting third, quickly grabbed second.
Jansrud, the World Cup Super-G winner who was fifth on the start list, could have clinched the crown by finishing ahead of Fill, but instead finished last to that point on 1:33.61, leaving both men to wait as other skiers tested the piste.
While rivals pushed Jansrud's place down the points list, none overtook the Italians from atop the podium.
Jansrud, the reigning Olympic Super-G champion who took a 2014 downhill bronze medal at Sochi, was the 2015 World Cup downhill and Super-G champion.