Collins made his debut at major championship at the 1997 World Championships, where he failed to qualify for the second round in the 100 m. He improved quickly, and at the 2000 Summer Olympics, he became the first athlete from his tiny nation to qualify for an Olympic final, finishing 7th in the 100 m. The next year, Collins would win Saint Kitts's first World Championship medal, when he tied for the bronze medal in the 200 m.
At the 2002 Commonwealth Games, he won his first major title, although not after a doping controversy. After the 100 m race, which Collins won after two other favourites pulled out of the final with an injury, he was tested positive for doping. However, it was found that the banned substance was part of the asthma medication Collins had been taking for several years, but had neglected to mention to the medical commission. Collins eventually was allowed to keep his title, and got away with a warning.
The 100 m at the 2003 World Championships became the biggest triumph of his career. With Olympic and World Champion Maurice Greene eliminated in the semi finals, the field was wide open. In a very close race, where the top four athletes finished within 0.02 seconds, Collins won and became the first World Champion from Saint Kitts and Nevis.