Born in the United States, where he first began competing in skiing events, Chappuis moved with his family to France as a child.

He won the gold medal in the 10km individual normal hill at the 2010 Winter Olympics in Vancouver, British Columbia, Canada after passing race leader Johnny Spillane in a dramatic sprint at the finish line.

"[2] Jason Lamy-Chappuis announced February 28, 2015, after winning his fifth world title in the team sprint with Francois Braud Falun he decided to take his retirement at the end of the 2014-2015 season to concentrate on his training airline pilot.

Since he had won cross-country competitions in the U.S. and ski jumping contests in France, he decided to continue pursuing both events through the Nordic combined.

[3] After establishing himself as a top regional skier in France, Lamy-Chappuis competed in his first international event in a European Cup Games competition in Planica, Slovenia during the 1999–2000 season.

In 2001–2002, he debuted on the French national junior team, leading to appearances in major competitions in Norway, Sweden, Slovenia, Italy, Finland, and Germany during his teenage years.

With five wins and nine podiums, Lamy-Chappuis entered the 2010 Winter Olympics in Vancouver, British Columbia, Canada as the World Cup leader in Nordic combined.

His winning time was 25:47.1 and came after a frantic finish that involved a last-minute push on his part to beat American Johnny Spillane by .4 seconds.

He attributed his win to Spillane's decision to slow down while entering the stadium, leaving Lamy-Chappuis with the opportunity to glide faster in the final stretch.