Mejía came through the Chelona youth academy and had a couple of seasons at Alianza before moving abroad to play for Honduran giants F.C.
In December 2007, that was reported that Mejía would make a comeback to football after a year long injury had prevented him from taking part in competitive games at any level.
[2] With the El Salvador U-21 team, Mejía won the 2002 Central American and Caribbean Games.
[3] He made his senior debut for El Salvador in a March 2001 friendly match against Panama and has earned a total of 19 caps, scoring 3 goals.
[6] His final international game was a September 2004 World Cup qualification match against the United States.