Gaitán moved to Mexico for the 2002 Apertura season, signing with Tigres UANL of the Primera División by request of Ricardo Ferretti. After scoring four goals in 15 games in his first season, he scored eight in the 2003 Clausura. Tigres was eliminated in semifinals of the Clausura 2003 playoffs by crosstown archrival Monterrey. After a remarkable Apertura 2003 season under coach Nery Pumpido, Gaitán and Tigres lost the finals against Pachuca in the Estadio Universitario. In the Apertura 2004, as revenge of the elimination on the Clausura 2003 playoffs, Tigres won the Clásico Regiomontano by the biggest difference ever, beating Monterrey by 6-2, he scored twice. Gaitán became the top goal-scorer of the 2005 Apertura. He was also named Best Player of the Clausura 2006 tournament. He scored a goal in the 2-1 victory of Tigres over city rival Monterrey in the finals of the 2006 InterLiga and secured 2006 Copa Libertadores. He was selected to wear the number 7, retired to honor team icon Gerónimo Barbadillo, in Copa Libertadores where regulations command that the number be used. Gaitán scored a total of four goals in Copa Libertadores with Tigres. When Tigres qualified for the Copa Libertadores, he wore the shirt of Rosario Central at the celebration. In October 2007, Gaitán, citing personal reasons, asked for a three-month license to be absent from the team until the end of the season. In December 2007, Club Necaxa announced the incorporation of Gaitán to the team, along with Omar Ortiz. Playing for Necaxa, he scored against Tigres and former archrival Monterrey. In 2010, Gaitán played briefly for Veracruz but was ceased due professional differences.
Gaitán was nicknamed in Mexico as "El Divino", due his gifted touch of the ball, vision and feel of the game. In Argentina, he was known as "El Chueco", for being left-footed. He is considered by Mexican media and fans as one of the greatest attacking midfielders ever to play in Mexico. Gaitán declined to play the 2006 World Cup with Mexico despite the call of then coach, Ricardo La Volpe. Being a midfielder, he finished the Apertura 2005 season as the top goal scorer of Liga MX with 14 goals. He is one of the top scorers of the Clasico Regiomontano, with eight goals. Gaitán did not achieve the League championship with Tigres, still, he is considered by the media and audience as an icon of the team, next to players such as Tomás Boy, Gerónimo Barbadillo, Osvaldo Batocletti, Claudio Núñez, Lucas Lobos and André-Pierre Gignac.