Thomas Pieters was born in Geel, Belgium in 1992. He started playing golf at the age of five, learning the game at the Witbos Golf Club in Noorderwijk, Belgium.
In summer 2013, Pieters decided to forgo his senior year at the University of Illinois and turn professional.

He made his debut on the European Tour in July at the Alstom Open de France, where he finished 29th; at the end of the year, he battled through all three stages of the European Tour Qualifying School taking the 20th card at the Final Stage, and qualified to play on the European Tour.

In August 2019, Pieters shot a 3-under 69 to become the first golfer to win the D+D Real Czech Masters for the second time, beating Adri Arnaus by one stroke.

Pieters claimed his fifth European Tour victory in November 2021 at the Portugal Masters. Two months later, Pieters won the Abu Dhabi HSBC Championship for his sixth European Tour win and first Rolex Series victory.

In February 2023, it was confirmed that Pieters had joined LIV Golf.