In 1999, Beltrán won the American League Rookie of the Year award, batting .293 with 22 home runs, 108 RBI and 27 stolen bases.

In the 2004 MLB playoffs, Beltrán tied Barry Bonds's single postseason record with 8 home runs. 

Carlos Beltrán played for Puerto Rico in the 2006 World Baseball Classic, joining Carlos Delgado, Bernie Williams, Javier Vazquez, Iván Rodríguez and others on the team managed by St. Louis Cardinals third base coach Jose Oquendo.

Beltrán's performance with the New York Mets in 2006 secured him a spot in the 2006 All-Star Game, his third. Also in 2006, Beltrán's 41 home runs tied the Mets' single season record for homers, matching Todd Hundley's total in 1996. Beltran's defense was also recognized during the 2006 season, as he received his first Gold Glove award.

Beltran won his 3rd straight Gold Glove award in the outfield for the Mets in 2008 season.

On December 22, 2011, Beltrán agreed to a two-year deal with the St. Louis Cardinals. On June 15, batting against his old team the Kansas City Royals, he became the first switch-hitter in MLB history to attain 300 home runs and 300 stolen bases, with his seventh stolen base in the second inning. He was a 2012 MLB All-Star and participated in the 2012 Home Run Derby.