Nicknamed "El Chunche", ('The Thing'), Montero made his debut for Costa Rica in 1985 and was part of the squad, that played in the 1990 FIFA World Cup held in Italy, and featured in all four games played. The defender collected 56 caps, scoring 3 goals He also represented his country at the 1991 and 1995 UNCAF Nations Cups as well as at the 1991 CONCACAF Gold Cup.