Thiem was born in Wiener Neustadt, Austria on 3 September 1993 to Wolfgang and Karin Thiem, both of whom are tennis coaches. He has a younger brother, Moritz Thiem, who is also a professional tennis player. Thiem grew up in Lichtenwörth and began playing tennis when he was six years old.

Thiem’s father, Wolfgang, began working as a coach at Günter Bresnik’s academy in Vienna in 1997, when Thiem was just three years old. Bresnik became Thiem’s coach formally from age nine.

Thiem reached an ITF Junior ranking of world No. 2 (combined singles and doubles) on 3 January 2011.

In 2011, Thiem received wild cards to the main draw of Kitzbühel, Bangkok and Vienna. In Vienna, Thiem recorded his first ATP win, over Thomas Muster, before losing to Steve Darcis in the second round.

In 2013, Thiem received a wild card to the main draw in Kitzbühel, where he made it through to the quarterfinals by defeating the fourth seed Jürgen Melzer in the second round. He lost in the quarterfinals to Albert Montañés in straight sets. Thiem reached his second quarterfinal of the year of an ATP 250 event at the Erste Bank Open. He was given a wild card, but lost to the top seed, Jo-Wilfried Tsonga, in three tough sets.

At the Madrid Open, Thiem qualified for a main tour event for the seventh time in 2014. In the second round he had the biggest win of his career when he defeated the world No. 3, Stan Wawrinka, in three sets. Thiem started his campaign at the French Open by beating Frenchman Paul-Henri Mathieu in straight sets. In the second round he faced world No. 1 and the defending champion, Rafael Nadal, but was defeated in straight sets, only winning seven games in the process. Thiem suffered consecutive first-round losses on grass at the Aegon Championships in London, to David Goffin, and at the 2014 Wimbledon Championships to Australian qualifier Luke Saville.

After Wimbledon, Thiem played at the International German Open where he reached the third round before being defeated by Leonardo Mayer. Thiem was seeded at an ATP tournament for the first time in his career at the Swiss Open Gstaad. Seeded eighth, he lost in the first round to wildcard Viktor Troicki. At the Austrian Open Kitzbühel Thiem was seeded fifth. In the semifinal he beat Juan Mónaco to reach his first ATP World Tour 250 final at the age of 20. In the final, he fell to David Goffin despite being a set up. Competing in his first ever US Open in 2014, Thiem reached the fourth round defeating 11th seed Ernests Gulbis, and 19th seed Feliciano López, before losing to sixth seed Tomáš Berdych. At the end of the 2014 season Thiem completed four weeks of mandatory national service with the Austrian military.

Thiem entered the Aegon Open Nottingham 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. Thiem competed at the third grand slam of the year, the Wimbledon Championships as the 32nd seed, marking the first time he had been seeded at a grand slam tournament. He defeated Israel’s Dudi Sela in four sets, marking his first ever win at Wimbledon. In the second round, Thiem lost a close five-setter against Fernando Verdasco, despite being 2–1 up in sets. After Wimbledon, he participated at the 2015 Croatia Open Umag as the fourth seed, which gave him a bye into the second round. 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 final, he defeated Portugal’s João Sousa in straight sets to claim his second career ATP World Tour title. A week later Thiem won his third title at the Swiss Open Gstaad, beating David Goffin in the final, winning back to back tournaments for the first time.

Thiem is a big fan of football and is a Chelsea supporter. 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. Thiem supports the environment, donating and raising awareness for 4ocean and the WWF. On ocean pollution he said “It’s one of the biggest problems nowadays that we face, with all the plastic pollution. I love nature and I’m trying to support this whenever I can.” Thiem was also part of his apparel sponsor Adidas’ 2019 Parley tennis collection campaign, the clothing of the collection being made from recycled plastic waste collected from beaches and coastlines with the aim to raise awareness and help tackle marine pollution.

His deliberate, yet aggressive playing style, particularly the long take-back on his groundstrokes, ability to sustain long baseline rallies and top-spin serves have greatly benefited his clay game. The Roland Garros website described him as an “heir to the throne.” He has beaten many high-ranked clay-court players on clay, recording four wins over Rafael Nadal on the surface. He defeated Nicolás Almagro and Nadal en route to his Argentina Open title, as well as Stan Wawrinka at the 2014 Madrid Open, Roger Federer at the 2016 Italian Open and the 2019 Madrid Open, and Novak Djokovic at the French Open both in 2017 and 2019. His mental game has also been praised, especially his tie-break win percentage.

Thiem began dating fellow tennis player Kristina Mladenovic in 2017. They publicly confirmed their relationship in May 2018 and split in November 2019.

In late December 2017, coach Galo Blanco was added to Thiem’s team. Thiem began his season at the Qatar ExxonMobil Open as the top seed. He reached the semifinals where he withdrew from his match against Gaël Monfils due to illness. At the Australian Open, Thiem lost in the fourth round against Tennys Sandgren. This was equal to his result of the previous year at the Australian Open. Thiem’s next tournament in mid-February 2018 saw him win his ninth ATP Tour title at the Argentina Open, his second in Buenos Aires. This was his first title in nearly a year. In Indian Wells, he won his second round match against Stefanos Tsitsipas. In his third-round match against Pablo Cuevas, he rolled his ankle in winning in the first set, later retiring from the match. He skipped Miami because of the hairline-fracture-ankle injury.

At Wimbledon, Thiem lost in the first round to Sam Querrey. Thiem played in Hamburg, losing in the quarterfinals to Andrey Rublev. The following week he won the 14th title of his career in Kitzbühel defeating Albert Ramos Viñolas in the final. At the US Open he lost to Thomas Fabbiano in the first round in four sets. At the China Open, Thiem defeated Andy Murray in straight sets to progress to the semifinals, where he defeated Karen Khachanov after being down a set and a break and coming back to win in three sets. With this win he qualified for the 2019 ATP Finals. In the final Thiem defeated Stefanos Tsitsipas to win his first title in Asia, fourth title in 2019 and 15th career title. At the Shanghai Masters Thiem reached the quarterfinals before being bested by Matteo Berrettini. For the first time in ten attempts, Thiem made past the quarterfinal stage at his home tournament in Vienna. He reached the final where he triumphed over Diego Schwartzman to claim the Vienna Open trophy, for his 16th career title.