At the Vienna Open, Thiem reached his second quarterfinal of the year losing to the top seed, Jo-Wilfried Tsonga, in a close three-set match.

[43] Thiem won his first career ATP Tour title in Nice, France,[44] defeating Nick Kyrgios, Ernests Gulbis and John Isner en route, winning a close three-setter against Argentina's Leonardo Mayer in the final.

[46] Thiem entered the Nottingham Open as the seventh seed, he defeated Malek Jaziri to claim his first win on grass in 2015, but was knocked out in the third round by Alexandr Dolgopolov.

After wins over Dušan Lajović and compatriot Andreas Haider-Maurer (after both players retired), Thiem advanced to the semifinals, where he defeated Gaël Monfils and earned himself a place in his third career final.

In the semifinals he was denied a place in his third consecutive final when he lost to German Philipp Kohlschreiber, which ended his winning streak of ten matches.

[59][60] In early March, Thiem participated in Austria's Davis Cup Group I first-round tie versus Portugal on indoor hard courts.

In late April, Thiem reached the ATP 250 final in Munich on outdoor clay, he played Philipp Kohlschreiber ultimately losing in three sets.

[68] At the US Open, Thiem beat Pablo Carreño Busta to reach the fourth round, where he retired against Juan Martín del Potro due to right knee injury.

[70] Thiem qualified for the ATP Finals for the first time losing his opening match to Novak Djokovic before he scored a win against Gaël Monfils.

[82] Thiem defeated Nadal in the quarterfinals of the Rome Masters 1000 tournament in two straight sets, before falling to Novak Djokovic in the semifinals.

During the round robin stage of the ATP Finals, Thiem defeated Pablo Carreño Busta in three sets, but lost to David Goffin and Grigor Dimitrov.

[111] In his third consecutive French Open semifinal, Thiem defeated unseeded Marco Cecchinato to advance to his first Grand Slam final.

[122] At the ATP Finals, Thiem was eliminated in the group stage after winning one match, against Kei Nishikori,[123] and losing his two others, against Kevin Anderson and Roger Federer.

[135] Just prior to the French Open Thiem parted with long time coach and manager Günter Bresnik, who he had been working with for 15 years.

[148] At the ATP Finals, Thiem defeated Roger Federer and Novak Djokovic in consecutive matches, and became the first player to qualify for the semifinals.

[185] His first tournament back was the Madrid Open, where he reached the semifinals by defeating Marcos Giron, Alex de Minaur and John Isner before losing to Alexander Zverev in straight sets.

As a result, on April 7, his spokesperson confirmed that Thiem had pulled out of the upcoming ATP Masters tournament in Monte Carlo and would return home to Austria.

[198] Unable to defend his semifinal points from 2021 at the Mutua Madrid Open following a first round loss to Andy Murray, he fell out of the top 150 in the rankings.

[204][205] At his home tournament in Kitzbühel Thiem reached the quarterfinals for the third week in a row defeating Alexander Shevchenko and Sebastian Ofner before losing to Yannick Hanfmann.

[210] Following the US Open, he made the final at the Challenger in Rennes, France, beating Gilles Simon, Ryan Peniston, Adrian Andreev, and Hugo Gaston, losing to former top 25 player Ugo Humbert.

At the Gijón Open he reached the semifinals of an ATP tournament for the second time in the season (after Gstaad) defeating fourth seed Francisco Cerundolo.

[218] During the South American clay court swing, he earned his first win of the season in the Argentina Open over Alex Molcan, but fell to Juan Pablo Varillas in the second round.

[225][226] At the Bavarian International Tennis Championships, Thiem defeated Constant Lestienne and Marc-Andrea Hüsler to reach the second quarterfinal of the season, where he lost to Taylor Fritz in straight sets.

[230] At the Austrian Open in Kitzbühel on home soil, Thiem defeated Facundo Bagnis, Zhang Zhizhen, and Arthur Rinderknech to set up a semifinal clash with Laslo Djere.

[240] He continued the Australian season by playing at the exhibition tournament in Kooyong, losing to Andy Murray but winning his match against Francisco Cerundolo, both in straight sets.

[243] In February, Thiem played for Austria at the World Group I play-offs in the Davis Cup, winning his singles match in straight sets against Michael Agwi.

[268] Thiem also won their 2019 ATP Finals round robin match in a third set tiebreak, Djokovic praising him afterwards for his "courageous tennis".

Thiem won their first three meetings, all in 2016 and on clay, including a first title fight in Nice before Zverev retaliated with a win on hard court in Beijing later in the year.

[301] He founded his own football club called 1.TFC Matzendorf in 2016, which consists of friends and fellow tennis players who come together a few times a year to play charity games.

The project, called Bio Bienen Apfel, aims to raise awareness about creating a habitat for bees in areas of Germany and Austria.