Rodriguez is considered one of the best all-around baseball players of all time. He is the youngest player ever to hit 500 home runs, breaking the record Jimmie Foxx set in 1939, and the youngest to hit 600, besting Babe Ruth's record by over a year.

In December 2007, Rodriguez and the Yankees agreed to a 10-year, $275 million contract. This contract was the richest contract in baseball history (breaking his previous record of $252 million).

In February 2009, after previously denying use of performance-enhancing drugs, including during a 2007 interview with Katie Couric on 60 Minutes, Rodriguez admitted to using steroids, saying he used them from 2001 to 2003 due to what he called "an enormous amount of pressure" to perform.

Rodriguez was born in the Washington Heights section of New York City to a Dominican family. When he was four, Rodriguez and his parents moved to the Dominican Republic, then to Miami, Florida. Rodriguez's favorite baseball players when he was growing up were Keith Hernandez, Dale Murphy, and Cal Ripken, and his favorite team was the New York Mets.

Rodriguez was a star shortstop at Miami's Westminster Christian High School. In 100 games he batted .419 with 90 steals. Westminster went on to win the high school national championship in his junior year. He was first team prep All-American as a senior, hitting .505 with 9 home runs, 36 RBIs, and 35 steals in 35 tries in 33 games, and was selected as the USA Baseball Junior Player of the Year and as Gatorade's national baseball student athlete of the year. Rodriguez was the first high school player to ever try out for Team USA in 1993, and was regarded as the top prospect in the country.

Rodriguez signed a letter of intent to play baseball for the University of Miami and was also recruited by the university to play quarterback for its football team. Rodriguez turned down Miami's baseball scholarship and never played college baseball, opting instead to sign with the Seattle Mariners after being selected in the first round of the amateur draft at the age of 17. In 2003, Rodriguez gave $3.9 million to the University of Miami to renovate its baseball stadium. The new facility will be named "Alex Rodriguez Park at Mark Light Field". Rodriguez remains an ardent University of Miami fan, and can frequently be found at Hurricane sporting events, as well as working out at the school's athletic facilities in the off-season. He received the University of Miami's Edward T. Foote II Alumnus of Distinction Award in 2007. Rodriguez had previously been named an "honorary alumnus" of the university in 2004. He is a member of the University of Miami's Board of Trustees.

Rodriguez was drafted first overall by the Seattle Mariners in 1993. He was signed by Roger Jongewaard right out of high school. In 1994, Rodriguez played for Seattle's AAA affiliate, the Calgary Cannons. In 32 games, he had 37 hits in 119 at bats for a .311 batting average. He also compiled 6 home runs and 21 runs batted in. Rodriguez rose rapidly through the Mariners organization, and made his major league debut as the starting shortstop on July 8, 1994, in Boston at 18 years, 11 months, and 11 days of age. He was just the third 18-year-old Major League shortstop since 1900. He was also the first 18-year-old Major League player in 10 years, and the youngest position player in Seattle history. His first Major League hit was a single off Sergio Valdez on July 9 at Fenway Park. Rodriguez's first Major League campaign lasted just one month; the season was cut short by the 1994 Major League Baseball strike.

Rodriguez then split most of 1995 between the Mariners and their AAA club, the Tacoma Rainiers. He connected for his first Major League home run off Kansas City's Tom Gordon on June 12. Rodriguez joined the Major League roster permanently in August, and got his first taste of postseason play, albeit in just two at-bats. Again, he was the youngest player in Major League Baseball.

The following year, Rodriguez took over as the Mariners' regular shortstop (SS) and emerged as a star player, hitting 36 HR, driving in 123 runs, and pacing the American League (AL) with a .358 batting average, the highest for an AL right-handed batter since Joe DiMaggio hit .381 in 1939 and the 3rd highest ever for a SS. At 21 years and one month, he was the 3rd youngest AL batting leader ever behind Al Kaline (20) in 1955 and Ty Cobb (20) in 1907, and the 3rd youngest player in history with 35+ homers. He was also the 1st major league SS to win a batting title since 1960, and the 1st in the AL since 1944, and at 20 years, 11 months, was the youngest SS in All-Star Game history. He also led the AL in runs (141), total bases (379), and doubles (54) and ranked among the league leaders in hits (2nd, 215), extra base hits (2nd, 91), multi-hit games (3rd, 65), slugging (4th, .631), RBI (8th, 123), and on-base percentage (8th, .414). Rodriguez posted the highest totals ever for a shortstop in runs, hits, doubles, extra base hits, and slugging, and tied most total bases, and established Seattle club records for average, runs, hits, doubles, and total bases, in a season that statistical analysts consider the best ever by an SS.

He was selected by both Sporting News and Associated Press as the Major League Player of the Year, and came close to becoming the youngest MVP (Most Valuable Player) in baseball history, finishing second to Juan González in one of the most controversial MVP elections in recent times. He finished three points behind González (290-287), matching the 2nd closest A.L. MVP voting in history.