At the 2003 Winter X Games, Jacobellis won bronze in slopestyle.
2006 Olympics
During the gold medal final of the Snowboard Cross at the 2006 Winter Olympics on February 17, 2006, Jacobellis was approaching the end of the course with a 43-meter, three-second lead over Tanja Frieden of Switzerland. On the second-to-last jump, Jacobellis attempted a method grab, landed on the edge of her snowboard, and fell. Frieden passed her to win the gold; Jacobellis recovered and settled for silver. In televised interviews, Jacobellis initially said the grab was meant to maintain stability, but later said that "I was having fun. Snowboarding is fun; and I wanted to share my enthusiasm with the crowd".
Post-Olympics
At the 2007 Winter X Games, Jacobellis lost the lead in a fall near the finish line in snowboardcross. She dropped halfpipe from her competition schedule in 2008, due to increasing injuries. Jacobellis regained the gold medal in snowboardcross at Winter X Games XII in 2008.
2010 Olympics
Jacobellis failed to progress to the medal round of Snowboard Cross at the 2010 Winter Olympics in Vancouver, as, early in her semifinal race, she landed badly during a jump, and to avoid a collision with another rider went through a gate, resulting in an automatic disqualification. She then slid off the course. She ended up 5th in the standings.
Post-Olympics
In 2011, Jacobellis won her fourth straight gold in snowboardcross at the Winter X Games, adding to her gold medals in 2008, 2009 and 2010.
2014 Olympics
Jacobellis failed to progress to the medal round of Snowboard Cross at the 2014 Winter Olympics in Sochi. She was leading the semi final race when she crashed. She finished in 7th place in the overall standings.
Post-Olympics
At the 2015 World Championship, Jacobellis won gold in the Snowboard Cross. She also won the and finished with a silver and two golds in the first World Cup races of the 2017–2018 season. The New York Times reported that in the period between the 2014 and 2018 Olympics, in addition to her training, surfing and other competition strategies, Jacobellis also began working with the mental skills coach Denise Shull.
2018 Olympics
Jacobellis made it to the final of the snowboard cross at the 2018 Winter Olympics in Pyeongchang County, South Korea and was leading most of the way, but ended up in 4th place by just.003 seconds and off the podium yet again.
