At the 2006 South American Games Castillo lost to Hamilton Ventura in the semifinals and ended up with a bronze medal. At the 2007 Pan American Games he won 15:5 against Carlos Negron, but lost to the eventual winner Eleider Alvarez 8:10 in the semifinal. He failed to qualify for the 2008 Olympics and went up to heavyweight, winning a silver at the 2011 Pan American Games. At the 2012 Olympic qualifier he lost 8:14 to Michael Hunter, but qualified for the Olympics on the strength of "two wins vs no-names". He lost in the first bout both at the 2012 and at the 2016 Olympics.