The young Cotto participated in several international tournaments, these include: The 1998 Junior World Championships that took place in Buenos Aires, where he finished in second place while competing in the Lightweight division. His three victories here were by points, the results were: Andrey Kolevin of Ukraine by points 15–3, Dana Laframboise of Canada by points 6–1, and Darius Jasevicius representing Lithuania 9–5. His only loss was to Anton Solopov of Russia by points with a score of 8–9. In 1999, Cotto competed in the Pan American Games that took place in Winnipeg, Manitoba, Canada. He only fought once in a loss to Dana Laframboise of Canada by points with a final score of 2–5. Following his participation in the Pan American tournament, Cotto was part of the Boxing World Championships in Houston, Texas. He lost his only fight by points to Robertas Nomeikas. In his final amateur tournament, Cotto represented Puerto Rico as a Light Welterweight at 2000 Sydney Olympic Games where he lost to Mahamadkadir Abdullayev of Uzbekistan by points. Cotto decided to turn professional after the loss to Abdulaev, ending his amateur career with a record of 125–23.