In his youth, Beltrán excelled in many sports, with volleyball and baseball being his favorites. At his father’s urging, he gave up volleyball to concentrate on baseball when he was seventeen. He was originally a shortstop before moving to the outfield. He graduated from Fernando Callejo High School in 1995.

The Kansas City Royals selected Beltrán in the second round of the 1995 Major League Baseball draft. After he signed, the Royals assigned him to the Gulf Coast Royals of the Rookie-level Gulf Coast League. Originally only hitting right-handed, he batted .276 with no home runs. During the off season, Beltrán taught himself to hit left-handed, with advice from New York Yankees outfielder Bernie Williams and Royals minor league coach Kevin Long. In 1996, he played for the Spokane Indians of the Class A-Short Season Northwest League, and the Lansing Lugnuts of the Class A Midwest League. In 1997 he spent the entire season playing for the Wilmington Blue Rocks of the Class A-Advanced Carolina League. He began the 1998 season with Wilmington, and received a promotion to the Wichita Wranglers of the Class AA Texas League.

Beltrán’s 41 home runs tied the Mets’ single season record for homers, matching Todd Hundley’s total in 1996. (This record was broken by Pete Alonso in 2019.) His 127 runs scored gave him sole possession of the Mets’ single season franchise mark. He and teammate José Reyes won the Silver Slugger Award at their respective positions. He also tied for the major league lead in times reached base on an error (13).

Beltrán made his major league debut on September 14, 1998, playing 15 games. Unlike many players, he never played in Triple-A. In 14 games of the 1998 baseball year, Beltrán got 16 hits, 5 doubles, 3 triples, and 7 RBIs with a .276 batting average during his time in the majors.

By 1999, he won the job as the Royals’ starting center fielder and leadoff hitter. He displayed significant power by midsummer, and was moved to the #3 slot in the batting order. Beltrán won the American League Rookie of the Year award, batting .293 with 22 home runs, 108 runs batted in (RBIs) and 27 stolen bases in 156 games played. On September 27, 1999, Beltrán made the final out at Tiger Stadium, striking out against relief pitcher Todd Jones as the Detroit Tigers beat the Royals 8–2.

Injuries restricted Beltrán to 98 games during the 2000 season and he slumped to .247, losing his center field position to the popular Johnny Damon. After Damon was traded to the Oakland Athletics following the season, Beltrán regained his job in 2001 and recaptured his rookie form. He batted .306 with 24 home runs and 101 RBIs in that season, followed by lines of .273-29-105 in 2002 and .307-26-100 in 2003.

In 2003, Beltrán batted .194 in April. His luck changed in 2004, as Beltrán began the year with eight home runs and 19 RBIs and was selected as American League Player of the Month for April.

On June 24, 2004, the Royals traded Beltrán to the Houston Astros in a three-team deal, which also sent relief pitcher Octavio Dotel from the Astros to the Oakland Athletics, while the Royals picked up Oakland minor leaguers (pitcher Mike Wood and third-baseman Mark Teahen) and Astros’ catcher John Buck.

For the rest of the 2004 season with the Astros, Beltrán played 90 games, batting .258 with 23 home runs, 53 RBI, and 28 stolen bases. Overall in 2004 combined with both teams he played for, Beltrán played 159 games with a .267 batting average, 38 home runs, 42 stolen bases, 104 RBI, and 121 runs scored.

In the 2004 playoffs, Beltrán tied Barry Bonds’ single post-season record with eight home runs. He hit one in each of the first four games of the National League Championship Series (NLCS) against the St. Louis Cardinals, including the game-winner in Game 4. Counting his two home-run performance in Game 5 of the previous playoff round in the National League Division Series (NLDS) against the Atlanta Braves, Beltrán clubbed at least one home run in a record-setting five consecutive postseason games, outnumbered only by Daniel Murphy’s home runs in six consecutive postseason games in 2015. In 12 games in the 2004 playoffs, Beltrán batted .435 with 14 RBIs and 21 runs scored.

Following the 2004 season, Beltrán became a free agent. The New York Yankees were tipped as favorites and Beltrán allegedly offered them a $19 million discount. The Yankees declined and the crosstown New York Mets signed him to a seven-year, $119-million contract, the biggest in franchise history at the time. It became the tenth contract in baseball history to surpass $100 million.

On August 11, 2005, in a game against the San Diego Padres at Petco Park, Beltrán was seriously injured after colliding head-to-head with fellow Mets outfielder Mike Cameron when both were diving to catch a ball in shallow right center field. Cameron missed the rest of the season with a concussion, temporary loss of vision, and two broken cheekbones. Beltrán suffered vertigo for a while, although both players eventually recovered.

Beltrán played for Puerto Rico in the 2006 World Baseball Classic, joining Carlos Delgado, Bernie Williams, Javier Vázquez, Iván Rodríguez and others on the team managed by St. Louis Cardinals third base coach José Oquendo. His 2006 season was an upgrade on his first year in New York. Boosted by 10 home runs in May, he surpassed his home run total from the previous year before the season was half over. Beltrán’s performance secured him a spot in the 2006 All-Star Game, his third. Five other Mets joined him, including three as starters. Beltrán was a standout for the NL as the only batter with multiple hits, along with two stolen bases. He scored the go-ahead run that gave the National League a 2–1 lead in the third inning, though the American League won the game. He hit grand slams in consecutive games on July 16 and 18, becoming the 23rd player to do so. Another grand slam at the end of July made him only the third Met to hit three in one season. Beltrán continued to produce with a walk-off home run against the St. Louis Cardinals on August 22, off Cardinals closer Jason Isringhausen. It was Beltrán’s second walk-off of the season, following a 16th-inning gamewinner against the Phillies.

In 2007, Beltrán hit below .230 from May to July. However, he improved in August and September, finishing with a .276 batting average and 112 RBIs. In July, he made his fourth All-Star Game appearance and upon the conclusion of the season, won his second straight Gold Glove award.

In 2008, Beltrán batted .284 with 27 home runs and 112 RBI. In the final game before the All-Star game, Beltrán hit his 15th home run of the season. On August 29, Beltrán collected all five RBIs for the Mets including a grand slam with two outs in the 9th to give the Mets a 5–2 lead. The Mets won this game 5–4. Beltrán hit the last and only Mets home run in the final regular season game at Shea Stadium (the last home run was by Dan Uggla). The home run was a two run shot that tied the game 2–2 against the Florida Marlins. Beltrán won his third straight Gold Glove award in the outfield for the Mets. He also won his second Fielding Bible Award as the top MLB center fielder in 2008.

Beltrán recorded his 1,000th RBI against Scott Olsen (Washington Nationals) with a triple in the third inning on April 24, 2009.

Since establishing his foundation, Beltrán began a fund with part of his salary, intending to establish a high school focused on developing young athletes. Construction of the Carlos Beltrán Baseball Academy began in 2009, in the municipality of Florida, Puerto Rico. Beltrán donated over $4 million to the academy, built on 20 acres (81,000 m) of land donated by the local government. The school opened in 2011, and graduated its first class in June 2013. It accepts students between the ages of 14 to 18 years, with a curriculum that includes instruction by MLB players.

On January 13, 2010, Beltrán had surgery on his knee and was originally expected to miss 8–12 weeks. The procedure was performed by Beltrán’s personal physician Dr. Richard Steadman. The Mets stated that the surgery was done without their consent, and the team expressed their disappointment with Beltrán’s decision. However, Beltrán’s agent, Scott Boras, claimed that the Mets consented to the procedure. Beltrán played his first game of the 2010 season on July 15.

Due to his declining defense, in 2011, Beltrán was moved from center field to right field. On May 12, 2011, playing against the Colorado Rockies, Beltrán hit three two-run home runs in a 9–5 Mets’ victory. It was the first three-home run game of his career, and he became only the eighth Mets hitter in history to hit three home runs in a single game.

On July 28, 2011, after he waived his no-trade clause, the Mets traded Beltrán to the San Francisco Giants in exchange for pitching prospect Zack Wheeler. The Mets also sent $4 million cash to the Giants to cover Beltrán’s remaining $6.5 million contract, which expired at the end of the 2011 season.

For the rest of the 2011 season with the Giants, Beltrán played 44 games batting .323 with 7 home runs and 18 RBI. Overall in 2011 combined with both teams he played for, Beltrán played 142 total games batting .300 with 22 home runs and 84 RBI.

On December 22, 2011, Beltrán agreed to a two-year deal with the St. Louis Cardinals worth $26 million which included a full no-trade clause. After Beltrán signed with the Cardinals, he attained numerous milestones, personal as well other firsts.

On April 4, 2012 Opening Day, Beltrán recorded the first-ever hit in a regular season game at Marlins Park against Josh Johnson of the Miami Marlins. Beltrán was named NL Player of the Week on May 14 after he hit .360 (9-for-25) with six home runs, 13 RBIs, eight runs, 30 total bases for a 1.200 slugging percentage and 1.648 OPS in the previous six games. He hit safely in five of the six games and homered in four of them. It was his ninth career weekly award, and sixth in the NL.

The Mets announced on June 18, 2012, that Beltrán was selected as the starting center fielder for 50th Anniversary Mets All-Time Team.

In the 2012 National League Wild Card Game, his first postseason game since 2006, Beltrán had 1 hit in 4 at-bats, scoring a run in the 4th inning. In the NLDS against the Nationals, Beltrán went 8-18 at the plate with 2 home runs and 4 RBI. Down 5-7 in the 9th inning in game 5 of the NLDS, Beltrán hit a leadoff double off of Drew Storen, eventually scoring two outs later on a Daniel Descalso single. The Cardinals would win the game 9-7.

In the 2012 National League Championship Series, Beltrán batted .300 with 2 RBI and 2 stolen bases. He played in 6 of the 7 games in the series, missing most of game 3 and all of game 4 after suffering a knee injury. Playing in his 3rd NLCS game 7 in his career, Beltrán went 1-4 at the plate as the Cardinals lost 0-9 to the Giants.

Beltrán is a Christian. While sliding into second base for his 300th steal, joining the 300–300 club on June 15, 2012, a cross necklace popped out of his jersey, and after the game, he told a reporter that “all the glory” was God’s. In 2004, Beltrán was one of 24 athletes who endorsed George W. Bush’s reelection campaign.

In 2013, Beltrán played in 145 games with a .296 batting average, 24 home runs and 84 RBI. Beltrán played in his 2,000th game on July 11, 2013. That same month, he was selected to his third straight All-Star Game. In October, Beltrán was the recipient of the Roberto Clemente Award, becoming the fourth Cardinals player to win it, joining Albert Pujols, Ozzie Smith, and Lou Brock.

In the 2013 National League Division Series against the Pirates, Beltrán had 4 hits in 18 at-bats, hitting 2 home runs and 6 RBI in the series. In game 1 of the 2013 National League Championship Series against the Dodgers, Beltrán hit a double at the bottom of the 3rd inning to tie the game 2-2. At the top of the 10th inning, with the game still tied 2-2, Beltrán threw out Mark Ellis at the plate after catching a fly ball, completing a double-play that prevented the Dodgers from taking the lead. At the bottom of the 13th inning, Beltrán hit a walk-off single off of Kenley Jansen, giving the Cardinals a 3-2 victory. For the whole NLCS, Beltrán had 6 hits and 6 RBI in 21 at-bats. The Cardinals won the series 4-2, and Beltrán advanced to the first World Series in his career.

On December 6, 2013, Beltrán agreed to a three-year, $45 million deal to join the New York Yankees, despite receiving a $48 million offer from another team. The deal became official on December 19, 2013.

On April 13, 2014, Beltrán played at first base for the first time in his professional career after Francisco Cervelli left the game due to a hamstring injury. On the night of May 12, 2014, Beltrán experienced soreness in his right elbow. It was revealed that the elbow had a bone spur and was immediately given a cortisone shot. He was placed on the 15-day disabled list on May 15, 2014. He was activated on June 5, 2014. To prevent any further damage to the elbow, he was used primarily as a designated hitter for the remainder of the season.

On September 16, 2014, Beltrán left the team for an indefinite period of time due to his wife’s miscarriage. Limited to 109 games in 2014, Beltrán batted .233 with 15 home runs and 49 RBI. On October 1, 2014, he underwent surgery to remove loose pieces and a bone spur in his right elbow, which required 12 weeks to recover. The procedure was performed by Yankees head team physician, Dr. Christopher Ahmad.

Beltrán got off to a slow start in 2015, batting around .200 through April. He slowly improved throughout the season and in September had a batting average over .280. On July 3, Beltrán was placed on the 15-day disabled list with an oblique injury. He was activated on July 19. On August 14 against the Blue Jays, Beltrán hit a pinch hit go-ahead 3 run home run in the 8th inning. It proved to be the game winner and temporarily put the Yankees back in 1st place. He reached 500 career doubles on August 31 against the Boston Red Sox. Beltrán ended the regular season with 19 home runs, 67 RBIs and a .276 average in 133 games.

In the 2015 American League Wild Card Game against the Astros, Beltrán had 1 hit in 4 at-bats as the Yankees fell to the Astros 3-0.

On April 25, 2016, Beltrán became the 84th player to make 10,000 career plate appearances. He collected his 2,473rd career hit on April 27 against the Texas Rangers to pass Ted Simmons for tenth place on the all-time list for switch-hitters. Beltrán hit his 400th career home run against the Chicago White Sox on May 15, the 54th player in MLB history to do, fourth switch hitter, the third Puerto Rican-born player, and the fifth to do so with 300 stolen bases and 500 doubles. On May 28, Beltrán homered for his 2,500th career hit off Matt Moore of the Tampa Bay Rays, joining Roberto Clemente, Ivan Rodriguez and Roberto Alomar as just the fourth Puerto Rican-born player to reach the milestone, and the 99th player overall to reach 2,500 hits. He became the fourth player, after Alex Rodriguez, Barry Bonds and Willie Mays, to reach 2,500 hits, 400 homers, 300 stolen bases and 1,000 walks.

On August 1, 2016, the Yankees traded Beltrán to the Texas Rangers for prospects Dillon Tate, Erik Swanson, and Nick Green. Beltrán hit his first home run for Texas on August 3 against Baltimore, also scoring his 1,500th run on the play. Towards the end of the season, Beltrán stated that he had “no plans to retire”, in contrast to his statements before the season. Beltrán ended the season with a .295 average, 29 home runs and 93 RBIs in 151 games between the Yankees and Rangers.

In the 2016 ALDS, Beltrán went 2-11 with 1 RBI in 3 games as the Rangers were swept by the Blue Jays 3-0.

On December 3, 2016, Beltrán signed a one-year, $16 million contract to return to the Houston Astros for the 2017 season as their designated hitter. On July 17, after not having played in the field in two months, his teammates held a mock funeral for his glove.

The Astros overcame one of Beltrán’s former teams, the Yankees, in the ALCS in seven games. As the Astros advanced to the World Series, it was the second of Beltrán’s career, where they opposed the Los Angeles Dodgers. During the series, Beltrán registered three plate appearances over three games, going 0–3. The Astros defeated the Dodgers in seven games, making Beltrán a World Series champion. Beltrán announced his retirement from playing on November 13, 2017.

Beltrán has appeared in the four editions of the World Baseball Classic (2006, 2009, 2013, 2017) for Team Puerto Rico. In the 2017 World Baseball Classic, he batted 4th in the lineup as their designated hitter. Following the conclusion of the tournament, which was won by United States upon beating Puerto Rico in the final, Beltrán was named to the 2017 All-World Baseball Classic team.

Following the 2017 season, the New York Yankees’ managerial position became available, for which Beltrán interviewed. The Yankees eventually selected Aaron Boone to be manager. In December 2018, the Yankees hired Beltrán as a special adviser to general manager Brian Cashman.

In 2017, Beltrán was named winner of Sports Illustrated’s inaugural Hope Award for his work in assisting Puerto Rico in the aftermath of Hurricane Maria.

On November 1, 2019, the Mets hired Beltrán as their manager to replace Mickey Callaway, signing him to a three-year contract with a club option for a fourth year. However, on January 16, 2020, before Beltrán ever managed a game, he and the Mets mutually agreed to part ways after he was the only then-player called out by name for his role in the Houston Astros sign stealing scandal. It is one of the few known instances in MLB’s history that a manager has been forced out before ever managing a regular season game.

Beltrán and his wife Jessica have two daughters and one son. Beltrán’s cousin Rey Fuentes is also a baseball player and also played for the Royals. A nephew, Matthew Lugo, was drafted by the Red Sox in 2019.