Cotto was taken as a little kid to the famous Bairoa Gym in Caguas, where Juan Carazo and Alberto Mercado also trained. There, he was able to develop into a top amateur fighter who won several international competitions and represented Puerto Rico at the 2000 Sydney Olympics. After being eliminated from those games in the first classificatory round, Cotto decided to turn professional.
As a professional, Cotto has a record of 17-0 with 13 knockout wins. He has been able to beat some strong competition, such as former world title challenger John Brown (by a 10 round decision, at the Oscar De La Hoya-Fernando Vargas fight undercard) and former world champion Cesar Cobrita Soto, by a knockout in round 11.
In 2001, Cotto suffered a dangerous injury that threatened his boxing career: As he was driving to the gymnasium at 5 am in the morning one day, he apparently fell asleep and had an accident, breaking his arm and requiring hospitalization.
On September 13, 2003, Cotto beat former title challenger Demetrio Ceballos by a knockout in round seven at Las Vegas. With this, he was ranked number one by the WBA in his division, which is lead, as of 2003, by Kostya Tszyu
Most boxing experts agree that Cotto has a good chance at becoming a world champion in the future.