Nicknamed "Tuma", Martínez made his debut for Costa Rica in a January 2001 FIFA World Cup qualification match against Guatemala and earned a total of 61 caps, scoring no goals. He represented his country in 26 FIFA World Cup qualification matches and played at both the 2002 and 2006 FIFA World Cups. He also played at the 2001 UNCAF Nations Cup as well as at the 2002 and 2003 CONCACAF Gold Cups.