Rebellin turned professional in 1992 and came to the attention of the cycling world with a string of strong performances during his early years. He suffers from asthma, a disease that will affect his whole career. In 1996 he gained further notice when he thrived in the
1996 Giro d'Italia. Riding for
Polti, the young Italian took stage seven and with it lead in the
general classification, giving him the pink jersey. He held the lead for six stages and finished the
Grand Tour sixth overall. Years later he said of the race, "I have won Classics, but the first important win was in the 1996 Giro, winning the maglia rosa with the stage."
Rebellin time trials in 2006
In 1997 he scored his first
UCI Road World Cup victories by winning the
Clásica de San Sebastián and the
Züri-Metzgete (then known as Grand Prix de Suisse). Over the following years he won many Italian classic races, such as the
Giro del Veneto and
Tre Valli Varesine. In 2001, he won the
Tirreno–Adriatico stage race.
During the 2004 season he amassed seven victories, including what was at the time an unprecedented treble win in the Ardennes classics, with wins in the
Amstel Gold Race,
La Flèche Wallonne and
Liège–Bastogne–Liège. Only one rider,
Philippe Gilbert, has repeated this feat since, in 2011. Rebellin also scored a number of podium places in top races such as
Paris–Nice and the
Clásica de San Sebastián. Despite these achievements, Rebellin did not win the
2004 UCI Road World Cup, which went to
In 2005, Rebellin fell short of his triumphs of 2004, but posted yet another solid year. Although he generally concentrated on classics and small tours, he was part of the
Gerolsteiner team in the
2005 Tour de France. With a number of solid performances throughout the season but without any individual victories, Rebellin finished as the third-highest ranked rider in the
UCI ProTour rankings. Apart from the ProTour races, he only won one race in the 2005 season, taking the first stage of the
Rebellin began the 2007 season leading
Alberto Contador moved him to second in the final stage to
Nice. He later finished second in
Amstel Gold Race and won the
Flèche Wallonne, which made him the
oldest ever winner of an UCI ProTour race. He finished second in the
UCI ProTour behind
Rebellin triumphed early in 2008 with an overall victory in the
Paris–Nice. He won the stage race by 3 seconds, ahead of
 He went on to win the
Tour du Haut Var and show strongly in the
Ardennes classics with a second place in the
Rebellin won the silver medal in the
Men's road race at the
2008 Summer Olympics in Beijing. He was a member of a six-man breakaway group and claimed second place in the sprint finish. This medal has now been revoked in light of his doping sentence by the
International Olympic Committee.
On 28 April 2015, at 43 years old, Rebellin won the
queen stage of the
Tour of Turkey, a mountaintop finish concluding in Elmali. He beat riders twenty years younger than him to accomplish this feat.
 With that performance, he grabbed the leader's jersey, but lost it to
Kristijan Durasek on Stage 6.
 He had to abandon on the last stage since he crashed after hitting a dog.