Signing with MLS At the age of 14, Adu became the youngest American ever to sign a major league professional contract in any team sport when he was chosen by D.C. United as the number one overall pick in the
2004 MLS SuperDraft. In order to allow Adu to play close to home, MLS assigned him to D.C. United on November 18, 2003, working a deal with the
Dallas Burn, who owned the top pick in the 2004 MLS SuperDraft. Dallas was compensated with a player allocation. Having already signed with D.C. United, Adu effectively became the first player selected in that draft, two months before it officially took place. D.C. United had previously signed American youngsters
Bobby Convey in 2000 and
Santino Quaranta in 2001—both aged 16 and the youngest players in MLS at the times of being drafted.
D.C. United On April 3, Adu came on in United's first game of the 2004 season against the
San Jose Earthquakes as a second-half substitute, making him the youngest player ever to appear in United States professional sports. On April 17, at the age of fourteen, Adu scored his first professional goal in the 75th minute of a 3–2 away loss against the
MetroStars. In doing so, he became the youngest player in MLS history to score a goal. In his first season as a pro, Adu finished the year with five goals and three assists, while playing in all 30 regular season games. Although briefly a starter, Adu was relegated to a substitute when D.C. United acquired central midfielder
Christian Gómez mid-season, and it was in this role that he appeared in United's MLS Cup victory. He played in three of four playoff games for D.C. United, assisting one goal during that time. Adu was criticized from a number of different angles in his first season as a professional. Some commentators suggested that Adu was too young to be playing professionally and that he needed more time to develop mentally and physically among players his own age. In his second season, he was suspended for one game after he complained about his playing time in the media. During November 2006, Adu had a trial with English club
Manchester United for two weeks, but he was not able to gain a work permit and so could not play in any competitive games, and only trained with several players from the
Manchester United academy during his two weeks. Continued development, especially of his defensive skills, helped Adu become a starting midfielder during the 2006 season. In addition, Adu had been chosen to take spot kicks during D.C. United's two penalty shootouts—scoring on both attempts. He was selected to the MLS All-Star team twice, once as a commissioner's choice and once as the coach's. He was selected for the Best XI of the 2006 MLS semifinals by
Soccer America magazine. In 2005, he was nominated for FIFPRO Young player of the year.
Real Salt Lake On December 11, 2006, D.C. United traded Adu and goalkeeper
Nick Rimando to Real Salt Lake in exchange for a
major allocation, goalkeeper
Jay Nolly, and future considerations. Adu made his debut for Real Salt Lake on April 7, 2007, playing the full 90 minutes in a 2–2 draw with
FC Dallas. He scored his first goal for the club on May 20, 2007, converting a
penalty kick in the 68th minute of a 2–1 loss to
FC Dallas. Adu went on to score his second goal with Salt Lake from another penalty in a 1–1 draw in an exhibition against
Boca Juniors. Adu was also captain of the
U-20 United States men's national team in the
2007 FIFA U-20 World Cup, where he made an impressive showing. After the conclusion of that tournament,
Benfica of the
Portuguese Liga secured Adu's rights from MLS for a transfer fee of $2 million.
Benfica On July 28, 2007, Adu opted out of playing for Real in their regular-season match, and later that day, boarded a plane to Portugal to negotiate with
Benfica. On July 30, Benfica issued an official statement announcing that Adu had been transferred to their club. On August 14, 2007, Adu made his debut with Benfica against
Copenhagen in a
UEFA Champions League qualifying match, coming into the game in the 37th minute as a substitute.
Loan to AS Monaco In July 2008, Adu joined Monégasque club
AS Monaco on a season-long loan, with an option to join the
Ligue 1 club permanently at the end of the deal, an option that was eventually declined by Monaco. In July 2009, after participating in the Gold Cup game against Honduras, he returned to Benfica for training.
Loan to Belenenses Adu was loaned to Portuguese club
Belenenses for the 2009–10 season. On October 13, Adu made his first league start in Portugal, a 1–0 loss to
Nacional. Adu was injured just before half time, and was substituted. In December 2009 Adu's season long loan was cut short.
Loan to Aris Adu signed a 12-month loan deal with Greek side
Aris in January 2010, joining fellow United States international
Eddie Johnson. Assigned squad number 11, Adu made his debut on January 31 and assisted on a 90th-minute goal by Johnson. He scored his first goal on February 14 against
Ergotelis.
Loan to Çaykur Rizespor On February 1, 2011, Adu moved to
Turkish Second Division side
Çaykur Rizespor on what was his fourth loan deal away from Benfica. Adu made his debut for his new club on February 20. He set up teammates Mithat Yaşar and
Gökhan Kaba with goals in a 3–0 win over
Orduspor and was named Man of the Match. Two weeks later, on March 6, Adu scored his first goal for his new club in a 1–0 win over
Gaziantep Büyükşehir Belediyespor.
Philadelphia Union After his contract with Benfica expired in August 2011, Adu returned to
Major League Soccer, signing with
Philadelphia Union, reuniting him with former
D.C. United and
United States national U-23 coach
Piotr Nowak. Though terms were not disclosed, as per club policy, it was stated that he was not a
designated player. Adu debuted for Philadelphia Union on August 13 in a match against
FC Dallas and scored his first goal for the club on September 7, 2011, against
New England Revolution.
Bahia On April 5, 2013, Adu joined
Bahia of Brazil. The deal also saw
Kléberson move in the opposite direction. He was released by the club on November 7, 2013.
2014 trials After his release from
Bahia he started a succession of unsuccessful trials around Europe. In February 2014, Adu began training with
Blackpool. At the end of February, they decided against offering Adu a contract, although they gave permission for him to continue training with the club to aid his fitness. In June 2014, Adu began training with Norwegian club
Stabæk, managed by former
United States national team coach
Bob Bradley. In July 2014, Adu joined Dutch club
AZ Alkmaar on trial, but he did not convince the club to offer him a contract.
Jagodina After a trial with AZ that ended without a contract, Adu signed with Serbian club
FK Jagodina on July 24, 2014. On July 25, it was announced that Adu had signed a one-and-a-half-year contract with Jagodina. Adu made his debut for Jagodina on September 24, 2014, coming on as a second-half substitute in a
Serbian Cup match against
FK BSK Borča. This was to be his only first-team appearance for the club. Adu was released by Jagodina, who opted not to renew his six-month contract, on December 21, 2014. Following Adu's release from Jagodina, Adu was linked with a move to the Swedish
Allsvenskan in February 2015.
KuPS On March 28, 2015,
KuPS announced the signing of Adu on a one-year contract, subject to passing a medical. Adu also played some games for KuPS' reserve team
SC Kufu in the Finnish
third division. On July 7 of the same year Adu exercised an option in his contract to terminate it.
Tampa Bay Rowdies On July 14, 2015,
Tampa Bay Rowdies of the
North American Soccer League announced the signing of Adu. Contract details of the signing were not disclosed. It was his 12th professional club. Adu made 13 appearances for the club before being released after the 2016 NASL season.
Las Vegas Lights FC Prior to the 2017 MLS season, Adu went on trial with the
Portland Timbers but was not offered a contract. Adu then went on trial with newly promoted Polish
Ekstraklasa side
Sandecja Nowy Sącz in August 2017. Adu joined the expansion
Las Vegas Lights FC on a trial basis prior to the 2018 season. Adu was not selected for either of the team's first two preseason matches. He was selected for the third and final preseason match against his former club
D.C. United, playing 30 minutes and notching an assist—the first assist recorded in club history and his first in nearly three years—in a 4–2 defeat. On March 15, 2018, Las Vegas added Adu to the regular season roster. Adu made 14 appearances for the Lights and scored one goal for the club during the 2018 campaign.
Österlen FF On October 14, 2020, after a two-year hiatus during which Adu worked as a youth football coach in Maryland, it was announced that Adu had joined
Österlen FF, recently promoted to the
third tier of Swedish football. After signing with the club, Adu expressed his excitement to play professional soccer again, observing that he "skipped a lot of steps in the past but now he gets a chance to do it right". On February 16, 2021, after only a month in Sweden, it was announced that Adu's contract had been terminated by the Österlen FF administration after the club deemed Adu not being physically or mentally fit enough to be competitive in
Ettan. Adu argued that internal conflict within the club was the reason for his exit. Adu told Swedish outlet
Sportbladet in a written statement: "There is some kind of power struggle going on in the club." He added: "The coach (Agim Sopi) says that I was signed without his approval, which he does not like. I have been in a similar situation before and it never ends happily. It is better to deal with it immediately." Österlen manager
Agim Sopi told Swedish outlet
Fotbollskanalen: "He has said that he wants to resume his career and then I think you want to show yourself from your best side, but he was totally untrained when he came here. His physical status was zero." Sopi further commented on Adu's stint at the club, stating: "We gave him a chance a month or so to see. But when you are away for so long. He has barely trained with us. He has had defects all along and I do not see that he has the mental strength required to recover." ==International career==