GRAND LEDGE (2000-2004)

             Horford holds seven school records, including most career points (1,239). As a senior, he was named "Class A Player of the Year" after averaging 21 points, 13 rebounds and five blocks per game. While at Grand Ledge, Horford played AAU basketball for the Michigan Mustangs, who were runners-up in the Adidas Big Time National Tournament. Considered a four-star recruit by Rivals.com, Horford was listed as the No. 7 power forward and the No. 36 player in the nation in 2004.

FLORIDA (2004-2007)

            He made an immediate impact for the Gators in 2004–05, starting at center in the front court with David Lee, and helped the Gators win the 2005 Southeastern Conference Tournament championship.

            The Gators surged through the 2005–06 season, winning the SEC championship for a second straight year. They entered the 2006 NCAA Tournament as the No. 3 seed. The Gators swept through the first four rounds to reach the Final Four. There they defeated George Mason to reach the final. In the final, they defeated UCLA for the 2006 championship behind Horford's 14 points and seven rebounds.

           On March 4, 2007, Horford’s junior year, against Kentucky, Horford became the fourth player on his team to score 1,000 career points. He required 14 points during the game to reach the milestone, and scored exactly 14.

           On April 2, 2007, the Gators became the first team to repeat as national champions since the 1991–92 Duke Blue Devils, and the first ever to do so with the same starting lineup. They defeated Oden and Ohio State in a rematch from the regular season, 84-75. Three days later, Horford declared for the NBA draft.

NBA (2007-present)

On June 28, 2007, Horford was selected by the Atlanta Hawks with the third overall pick in the 2007 NBA draft. 2007–2016 Atlanta Hawks, 2016–2019 Boston Celtics, 2019–2020 Philadelphia 76ers, 2020–2021 Oklahoma City Thunder, 2021–present Boston Celtics.

5× NBA All-Star (2010, 2011, 2015, 2016, 2018), All-NBA Third Team (2011), NBA All-Defensive Second Team (2018), NBA All-Rookie First Team (2008), 2× NCAA champion (2006, 2007), Second-team All-American – NABC (2007), Third-team All-American – AP (2007), SEC Tournament MVP (2007)

             On May 29, 2022, Horford reached the NBA Finals for the first time in his 15-year career when the Celtics defeated the Miami Heat in Game 7 of the Eastern Conference Finals, 100–96. Before doing so, he set a record for the most playoff games without a Finals appearance, with 141. He also became the first Dominican to reach the NBA Finals. In Game 1 of the Finals, Horford led the Celtics to a 120–108 win over the Golden State Warriors with 26 points and six rebounds. During the game, he hit six 3-pointers, setting an NBA record for most threes made by a player in his Finals debut. 

With the arrival of Kristaps Porziņģis during the 2023 offseason, for the first time in his professional career, Horford came off the bench. With Porzingis getting injured, he returned as the Celtics' starting center for the majority of the playoffs. On May 15, 2024, in Game 5 of the Eastern Conference Semifinals, Horford became the first player in NBA history to record 10+ rebounds, 5+ three-pointers, 5+ assists, and 3+ blocks, as he did in a series-clinching 113–98 victory over the Cleveland Cavaliers. In Game 3 of the Eastern Conference Finals against the Indiana Pacers, Horford scored 23 points on a career-high seven three-pointers in a 114–111 comeback victory. The Celtics won the series in four games and advanced to the 2024 NBA Finals, where he started all five games as they defeated the Dallas Mavericks, giving Horford his first NBA championship in his 186th career playoff game. This made him the first Dominican player to win a championship in the NBA.