The next week, he received a wildcard into the 2018 Moselle Open, where in reached the second round by defeating Bernard Tomic before falling to Nikoloz Basilashvili.

Once in the main draw, he drew lucky loser Pablo Cuevas, defeating him in straight sets for his first ATP match win of the year.

After the Australian Open, Humbert reached the semifinals in Quimper as the second seed, defeating Raúl Brancaccio, Oscar Otte and Tobias Kamke.

At the challenger in Cherbourg, Humbert reached the final by defeating Elliot Benchetrit, Alexey Vatutin, Otte and Mats Moraing.

The week after, Humbert was awarded a wildcard into Marseilles, where he defeated Ernests Gulbis, Borna Ćorić and Matthias Bachinger to reach his first tour-level semifinal, where he lost to Mikhail Kukushkin.

In Lyon, Humbert would pick up his only victory on clay in his year, beating Cameron Norrie in the first round before losing to Denis Shapovalov.

Then, he defeated Marcel Granollers and 19th seed Félix Auger-Aliassime in straight sets to reach the fourth round of a Grand Slam for the first time in his career.

Humbert's good form continued into Newport, where he reached his second semifinal of the year, beating Ramkumar Ramanathan and Ilya Ivashka.

There, he defeated Marek Gengel, Hugo Grenier, Ruben Bemelmans and Blaž Kavčič to reach the second Challenger final of his year.

After the victory, however, Humbert lost two tournaments in a row in Metz to Yannick Maden and Orléans to Sergiy Stakhovsky, but then won his first match in Mouilleron le Captif against Robin Haase before losing to Jiří Veselý.

In Antwerp, he defeated Jozef Kovalík, then upset second seed and home favourite David Goffin in straight sets to reach the third ATP Tour-level quarterfinal of his season.

After his run in Antwerp, Humbert played Brest, where, as the top seed, he defeated Maxime Janvier, Evgeny Karlovskiy, Antoine Hoang and Norbert Gombos to reach the final.

At the Next Gen Finals in Milan, Humbert lost to Mikael Ymer and Frances Tiafoe before defeating eventual champion Jannik Sinner.

[16] He reached his first ATP Tour final at the ASB Classic, beating en route two top 20 players, Denis Shapovalov[17] and John Isner.

Competing in Acapulco, he won his first-round match when his opponent, sixth seed and defending champion, Nick Kyrgios, retired due to a left wrist injury.

[25] As the top seed at the Oracle Challenger Series in Indian Wells, he was upset in the second round by eventual finalist, Jack Sock.

Seeded seventh at the first edition of the Mallorca Championships, he withdrew from his second-round match against Sam Querrey due to food poisoning.

[65] At the end of September, as the top seed at the Open d'Orléans, an ATP Challenger Tour event, he lost in the first round to compatriot Quentin Halys.

[66] On 1 November 2021, Humbert ended his season early due to injury, having withdrawn previously from Indian Wells, Antwerp and the Paris Masters.

[94] He reached the third round of the Australian Open for the first time at this Major defeating compatriot Richard Gasquet and lucky loser Denis Kudla.

[98] Representing France in the Davis Cup tie against Hungary, he won both of his matches by beating Márton Fucsovics and Fábián Marozsán.

[101] Playing as a wildcard at the Open Sud de France, he was forced to retire during his first-round match against fifth seed and friend, Alejandro Davidovich Fokina, due to a right leg injury after suffering a nasty fall.

En route to the title, in the quarterfinals, he won the second longest best-of-three matches on the ITF circuit against Taro Daniel lasting close to four and a half hours.

He reached his fourth career final defeating wildcard Fabio Fognini [118] and eventually won the title triumphing over Alexander Shevchenko.

[120] A few weeks later, Humbert won his sixth title, and second at the ATP 500 level, at the Dubai Championships, defeating seventh seed Alexander Bublik in the final.

[123] However, he would not see the same success at any other clay court tournament he entered, and only won one other match at Madrid, and losing in the first round in Lyon and the French Open.

[citation needed] At Wimbledon, Humbert reached the fourth round for the second time in his career, defeating Alexander Shevchenko, Botic van de Zandschulp and Brandon Nakashima before losing to Carlos Alcaraz.

[citation needed] He reached his seventh final at the 2024 Japan Open Tennis Championships, where he lost to compatriot Arthur Fils.

[citation needed] Seeded 15th at the 2024 Rolex Paris Masters, Humbert beat Brandon Nakashima and Marcos Giron to reach the third round.

En route to his 2024 Open 13 Provence and Dubai titles he was also coached by his girlfriend and fellow tennis player Tessah Andrianjafitrimo.