Castro made his international debut for the Mexico national football team in Los Angeles in a friendly match against Argentina on February 4, 2003. Ricardo La Volpe played him as a Right Winger as usual, but as a midfielder instead of defender. He played his first World Cup match against Portugal in Germany, a game which the Mexicans lost 2-1. Despite the team losing the match, Castro helped his country reach the Round of 16 where they played against Argentina. Since then, he has been called up to play friendly matches. He was even called up to play the 2007 editions of the Gold Cup and Copa América for Mexico. Recently, he was called up by Mexico coach Javier Aguirre for the 2009 Gold Cup. He scored his only international goal against the United States in the 2009 CONCACAF Gold Cup Final.