2002–2009 Brown officially turned pro in April 2002 at the age of 17 and began representing Jamaica. Between 2002 and 2009, Brown reached 11 ITF singles finals and 32 ITF doubles finals, winning 3 singles titles and 16 doubles titles. Brown made his ATP debut at the
2003 Hall of Fame Open after qualifying for the main draw. He lost in the first round to
Bob Bryan in three sets. Brown reached his first Challenger final at the
2009 Baden Open where he lost to
Florian Mayer in straight sets. Three months later, he won his first Challenger title at the
2009 Samarkand Challenger defeating
Jonathan Dasnières de Veigy in the final. For the rest of 2009, he made four more Challenger finals including one doubles final. These results helped increase his ranking from 494 at the start of the year to 144 at year's end.
2010–2019 in 2010 2010 is considered to be Brown's breakout year. At the
SA Tennis Open in
Johannesburg, South Africa, he made his first ATP main-draw appearance since 2003, defeating fourth seed
Marco Chiudinelli and No. 139
Laurent Recouderc to reach the quarterfinals, where he lost to eventual runner-up
Stéphane Robert. He became the second Jamaican after
Doug Burke at the
1989 BP National Championships in
Wellington, New Zealand, to reach the quarterfinals of an ATP tournament. On May 17, 2010, Brown reached the top 100 for the first time, debuting at No. 99. In June, he competed in his third ATP main draw at the
Queen's Club Championships in London, defeating
Frank Dancevic in three sets before losing to
Denis Istomin in the second round. It was reported at the time that lack of funding and support from the Jamaican Tennis Association had tempted him to switch national association to Great Britain, his paternal grandmother being British. Later that month, Brown made his Grand Slam debut at
Wimbledon after receiving direct entry into the main draw. He lost in the first round to 16th seed
Jürgen Melzer in four sets. After another ATP quarterfinal at the
2010 Hall of Fame Open, Brown received direct entry into the
US Open and won his opening match against
Rubén Ramírez Hidalgo to record his first Grand Slam win. He lost in the second round to world No. 4
Andy Murray in straight sets. In September 2010, Brown won his first ATP doubles title at the
2010 Open de Moselle partnering
Rogier Wassen. In October 2010, Brown began representing Germany and competed under the German flag for the first time at the
Challenger Eckental, where he reached the semifinals before losing to eventual champion
Igor Sijsling. His first title success playing under the German flag came a week later at the
Lambertz Open, defeating Sijsling in the final. Brown won his second ATP doubles title at the
2012 Grand Prix Hassan II partnering
Paul Hanley. Brown partnered
Jonathan Marray at the
2012 French Open; they lost in the first round. Brown/Marray also reached four Challenger tour finals in 2012, winning two in
Bosnia and
Italy. At
2013 Wimbledon, Brown qualified for the main draw and went all the way to the third round defeating
Guillermo García López and former champion
Lleyton Hewitt before falling to
Adrian Mannarino in straight sets. At the
2014 U.S. Men's Clay Court Championships, Brown upset first seed and world No. 9
John Isner in the second round to claim his first-ever win over a top 10 player. He would lose to
Sam Querrey in the next round. . In 2014 he achieved his most significant career win by defeating world No. 1 Rafael Nadal at the
Halle Open as a wildcard. At
Wimbledon in 2015 Brown came through qualifying without dropping a set. After beating
Yen-hsun Lu in the first round, Brown then upset, for the second time in his career, 10th seed and two-time champion
Rafael Nadal in four sets in the second round, before losing to
Victor Troicki in four sets in the next round. In January 2016, Brown played world No. 1
Novak Djokovic at the
Qatar Open. He lost in straight sets. Brown reached his first singles semifinal on the ATP World Tour at the
2016 Open Sud de France after having lost eight consecutive quarterfinal matches. There, he lost against top seed and eventual champion
Richard Gasquet in three sets. Brown reached a career debut second round of the
French Open in 2016. After winning the
2016 Aegon Manchester Trophy, Brown received a wild card for the
2016 Wimbledon Championships. There, he defeated
Dušan Lajović in the first round before losing to
Nick Kyrgios in the second. Both matches were decided in five sets. Brown made his second ATP singles semifinal at the
2016 Swiss Open Gstaad but lost to top seed and eventual champion
Feliciano López in three sets. Brown competed in the first round of the
2016 Summer Olympics against
Thomaz Bellucci of Brazil. Brown was leading 6–4, 4–4 when he went down with an ankle injury. Medical staff taped him, he returned to the match playing two points. Bellucci increased the score to 4–5 in the second set. Brown could not return play and retired in tears. On October 10, 2016, Brown achieved a career-high singles ranking of 64 and ended the year ranked 72. Brown upset world No. 7
Marin Čilić at the
2017 Open Sud de France. He would retire after just one game of play against
Benoît Paire in the next round due to a back injury. Brown lost in straight sets to
Andy Murray at Wimbledon in 2017 in the second round. Brown qualified for the
2018 Australian Open in what would be his last grand slam to date. He lost to
João Sousa in the first round in five sets. At the
2018 Open Sud de France, Brown was one game away from defeating
Nicolas Mahut in the first round, but he sustained a back injury and could not continue to play giving Mahut the victory. He left the court in tears. In April 2019, Brown reclaimed an ATP Challenger singles title from three years previous at the
Mouratoglou Open in Sophia Antipolis, winning the final over
Filip Krajinović in straight sets. On 13 June 2019, Brown upset compatriot and world No. 5
Alexander Zverev at the
2019 Stuttgart Open in the second round. Following this victory, he lost in a third-set tiebreaker to
Félix Auger-Aliassime in the quarterfinal.
2020–2022 Brown reached the qualifying competition of the
2020 French Open Qualifying and the
2021 Australian Open Qualifying before being eliminated both times. Throughout 2021, Brown seemed to focus less on singles and more on doubles as he was competing in more doubles events than singles and was finding more success as he was reaching a handful of quarterfinals and semifinals in challenger events and ATP events. Brown received a wildcard into the
2021 Stuttgart Open due to his performance in the previous edition. He lost in the first round to
Nikoloz Basilashvili in straight sets. This was his last professional singles match. In 2022, Brown stopped representing Germany and returned to representing Jamaica in tournaments.
2024: Retirement Due to persistent injuries since the start of 2018, Brown announced in January 2024 that he would retire from professional tennis at the end of the
2024 season. ==Davis Cup==