Cienfuegos was an important player for El Salvador national team, joining the team as a teenager, and continuing to lead his national side well into his thirties. He has earned a total of 68 caps, scoring 8 goals, all of them during a home game. He has represented his country in a massive 32 FIFA World Cup qualification matches and played at the 1995 UNCAF Nations Cup as well as the 1996 and 1998 CONCACAF Gold Cups.