[4] The highlight of his junior career came at the 2012 US Open when he partnered with fellow Australian Nick Kyrgios to reach the doubles final.

In 2013, Thompson made his debut on the professional circuit in qualifying at the 2013 Apia International Sydney where he lost to world number 81 Guillermo García López.

After receiving a wild card he won his first professional match in qualifying at the 2013 Australian Open against Nicolas Renavand in the third set.

[5] Thompson later made his Grand Slam debut at the 2014 Australian Open after winning the wildcard play off against Benjamin Mitchell on 15 December 2013.

From September to November, Thompson competed in eight challenger tournaments throughout China, USA, Australia and Japan, with the second round being his best result.

Thompson earned a wild card into the 2015 Australian Open but lost in round 1 to João Sousa in straight sets.

In October, Thompson made the finals of the Ho Chi Minh City and Traralgon Challengers, further increasing his ranking.

He was then given a wild card into the Sydney International, where he scored first his ATP World Tour win, when his opponent Martin Kližan retired when trailing 6–2, 4–0.

[12] Thompson was awarded a wild card into the French Open, where he won his first main draw Grand Slam match against Laslo Đere.

Thompson commenced the year at the 2017 Brisbane International, where he defeated Elias Ymer and David Ferrer to make his first ATP World Tour quarterfinal.

Thompson partnered Thanasi Kokkinakis in the doubles, where they reached the final, defeating Sam Querrey and Gilles Müller.

At the 2017 Apia International Sydney, Thompson defeated Nikoloz Basilashvili before losing to Philipp Kohlschreiber in round 2.

He lost in the first round of both Indian Wells and the Miami Masters, before returning to Australia when he defeated Jack Sock in the quarterfinals of the 2017 Davis Cup.

Entering the Queen's Club Championships draw as a lucky loser, Thompson unexpectedly defeated the world No.1 Andy Murray in round one.

In August, Thompson came within two points of defeating eventual champion and world number 8 Alexander Zverev at the Citi Open[18] before making the final of the Vancouver Challenger.

Thompson lost to Cameron Norrie in round 1 of the US Open and to Dominic Thiem in the Australia v Austria 2018 Davis Cup World Group play-offs.

At the Australian Open, as a wildcard, Thompson defeated Feliciano López and lost to Andreas Seppi in the second round.

The following month, Thompson defeated Grigor Dimitrov in a round three match at the 2019 Miami Open to reach the last 16 at a Masters 1000 tournament for the first time.

At the 2020 Australian Open, Thompson beat Alexander Bublik in straight sets, but lost to 12th seed Fabio Fognini in a match lasting over 4 hours.

Thompson achieved his best Grand Slam result to date by reaching the fourth round of the 2020 US Open, beating Stefano Travaglia, Egor Gerasimov and Mikhail Kukushkin before losing to 27th seed Borna Ćorić.

Thompson partnered fellow Australian Max Purcell in the doubles event, but was eliminated in the second round by eventual finalists Hugo Nys and Jan Zielinski.

[32] At his home tournament in 2024 Brisbane International having got a walkover from fourth seed Ugo Humbert, to get to the quarterfinals, he reached his first hardcourt semifinal, defeating former world No.

[35] The following week, he reached another quarterfinal at the 2024 Delray Beach Open but lost to another American fourth seed Tommy Paul and moved into top 40 in the singles rankings on 19 February 2024.

[36] He reached back-to-back-to-back quarterfinals in three weeks, this time at the 2024 Los Cabos Open defeating wildcard Ernesto Escobedo and his cousin, qualifier Emilio Nava.

[41][42] In April, as defending champions,[43] the pair Thompson and Purcell won their fourth title as a team at the 2024 U.S. Men's Clay Court Championships.

[45] Partnering former Wimbledon doubles champion Max Purcell, he reached his first Grand Slam final at the All England Club.

They were defeated in the final by first time Major champions Henry Patten and Harri Heliovaara in a three-setter with three tiebreaks, after having three match points in the third set.

[citation needed] Following a quarterfinal showing at the 2024 Mubadala Citi DC Open with a win over ninth seed Giovanni Mpetshi Perricard, he reached the top 30 in the singles rankings on 5 August 2024.

[49] With Purcell, he reached a second Grand Slam final in doubles at the US Open, defeating American duo and 13th seeds Nathaniel Lammons and Jackson Withrow.

[50] They defeated tenth seeds Kevin Krawietz and Tim Pütz lifting their first Grand Slam trophy as a team, and the first at this level for Thompson and second for Purcell.