Both his mother, Juanita, and father, Phil, were heroin addicts, and died of AIDS-related illnesses before Dixon was 17 years old. He was then raised by his grandparents Roberta and Warnick Graves in Baltimore, Maryland.
Dixon played in 34 games his freshman year and averaged 7.4 points per game. He made improvements in his sophomore year as he averaged 18 points per game and was selected to the All-ACC team.
Both Dixon and the Terps entered the 2000-2001 season with high expectations. The Terps began ranked in the top ten in most major polls while Dixon was a candidate for the Naismith Award Player of the Year award and the Wooden Award Player of the Year award. Dixon helped lead the Terps to their first ever Final Four appearance where the team lost to Duke. Dixon ended the season averaging 18.2 points per game and was again elected to the All-ACC first team.
He became Maryland's all-time scoring leader when he scored 29 points against Wisconsin to help Maryland advance to the Sweet Sixteen, passing Len Bias (2,149 points). He also became the only player in NCAA history to accumulate 2,000 points, 300 steals and 200 three-point field goals. In addition to leaving Maryland as the school's all-time scoring leader, Dixon also left as the Terrapins' all-time leader in three-pointers made (239) and attempted (615). He is second on Maryland's all-time steals list with 333 and third in free-throw percentage (.850). Dixon also stands as Maryland's all-time NCAA Tournament scoring leader with 294. Upon completion of his career, Dixon's #3 jersey was honored and now hangs in the XFINITY Center. In 2002, Juan Dixon was honored as a part of the ACC 50th Anniversary men's basketball team, one of only 8 Terrapins selected to the 50-man team. After his senior season, Dixon was featured on the cover of a video game, NCAA Final Four
Dixon was drafted 17th overall by the Washington Wizards in the 2002 NBA Draft. He spent the first three years of his NBA career with the Wizards. In his final season in Washington (2004–2005), he averaged eight points per game, including a career-high 35 points in Game 4 of the Eastern Conference Quarterfinals against the Chicago Bulls. Dixon signed as a free agent with the Portland Trail Blazers during the summer of 2005. Soon after, his Wizards and Terrapins teammate and friend Steve Blake signed with Portland as well. In his first game back in D.C., Dixon was given a standing ovation from the Verizon Center crowd upon coming off the bench towards the end of the first quarter. In Dixon's first year with the Blazers, he started 42 times and played in 76 games. In his last year with the Wizards, he only started four games and played in 63. He also increased his scoring, assists, and shooting percentage considerably in Portland. However, he was later traded at the 2007 NBA trade deadline to Toronto for Fred Jones and future considerations.