After going undrafted in the 2017 NBA draft, Caupain signed a summer league contract with the NBA's Toronto Raptors and received a subsequent training camp invite from the Orlando Magic on August 31, however, he was waived on October 13.
Ten days later, he was acquired by the Lakeland Magic of the NBA G League, averaging 15.8 points, 7.5 rebounds, 5.7 assists and 1.4 steals in 51 games.

On April 4, 2018, after the conclusion of the G League season, Caupain signed with G.S.A. Udine of the Italian Serie A2 Basket.

On July 11, 2018, Caupain signed a two-way contract with the Orlando Magic.
Under the terms of the deal, Caupain split time with Orlando and their NBA G League affiliate, the Lakeland Magic.
Caupain made his NBA debut on December 31, 2018 in a 125-100 loss to the Charlotte Hornets, scoring five points with two assists in five minutes of playing time.

On September 12, 2019, Caupain joined the Portland Trail Blazers for training camp.
On October 18, 2019, the Trail Blazers waived Caupain.

On November 3, 2019, Caupain signed a one-year deal with Hapoel Holon of the Israeli Premier League.
 On December 28, 2019, Caupain recorded 23 points, while shooting 8-of-12 from the field, along with six rebounds and four assists in an 84–91 loss to Hapoel Jerusalem.
On February 6, 2020, he parted ways with Holon.

On February 21, 2020, Caupain signed with Filou Oostende of the Belgian Pro Basketball League.

On July 31, 2020, he has signed with ratiopharm Ulm of the German Basketball Bundesliga.
After going undrafted in the 2017 NBA draft, Caupain signed a summer league contract with the NBA's Toronto Raptors and received a subsequent training camp invite from the Orlando Magic on August 31, however, he was waived on October 13. Ten days later, he was acquired by the Lakeland Magic of the NBA G League, averaging 15.8 points, 7.5 rebounds, 5.7 assists and 1.4 steals in 51 games.
On April 4, 2018, after the conclusion of the G League season, Caupain signed with G.S.A. Udine of the Italian Serie A2 Basket. 
On July 11, 2018, Caupain signed a two-way contract with the Orlando Magic. Under the terms of the deal, Caupain split time with Orlando and their NBA G League affiliate, the Lakeland Magic. Caupain made his NBA debut on December 31, 2018 in a 125-100 loss to the Charlotte Hornets, scoring five points with two assists in five minutes of playing time.
On September 12, 2019, Caupain joined the Portland Trail Blazers for training camp. On October 18, 2019, the Trail Blazers waived Caupain.
On November 3, 2019, Caupain signed a one-year deal with Hapoel Holon of the Israeli Premier League.  On December 28, 2019, Caupain recorded 23 points, while shooting 8-of-12 from the field, along with six rebounds and four assists in an 84–91 loss to Hapoel Jerusalem. On February 6, 2020, he parted ways with Holon.
On February 21, 2020, Caupain signed with Filou Oostende of the Belgian Pro Basketball League.
On July 31, 2020, he has signed with ratiopharm Ulm of the German Basketball Bundesliga.
Troy Caupain