From 2008 to 2011, Toupane spent time with the Élan Béarnais Pau-Orthez and SIG Strasbourg Under 21 teams, before joining the SIG Strasbourg senior squad for the 2011–12 LNB Pro A season. As a rookie, he averaged 2.5 points and 1.4 rebounds, in 22 French Pro A League games. In the 2012–13 season, Toupane averaged 3.9 points and 1.9 rebounds per game, in 35 French Pro A League games, as he helped Strasbourg reach the French Leaders Cup Final. He was considerably more effective the following season, as he averaged 6.1 points and 2.5 rebounds per game, in 41 French Pro A League games. Following the 2013–14 season, Toupane entered the 2014 NBA draft, but he was not selected. He then competed in the 2014 NBA Summer League, for the Dallas Mavericks' summer league squad, where he averaged 3.5 points and 2.0 rebounds per game, in four games. He returned to Strasbourg following the Summer League, and in the 2014–15 season, Toupane averaged 7.5 points, 2.5 rebounds and 1.4 assists per game, in 42 Pro A games. Strasbourg finished as the regular season leaders for a second straight year in 2015, and also won the French Cup and the French Leaders Cup.
On July 23, 2015, Toupane signed with the Toronto Raptors, after averaging 4.3 points and 1.7 rebounds, in three Summer League games for the team. On October 24, 2015, he was waived by the Raptors, after appearing in two NBA preseason games. On October 31, 2015, Toupane was acquired by the Raptors 905, of the NBA Development League, as an affiliate player of Toronto. On November 19, he made his debut for the Raptors 905 in a 109–104 loss to the Maine Red Claws, recording 17 points, 10 rebounds, four assists and one steal, in 30 minutes of playing time.
On March 3, 2016, Toupane signed a 10-day contract with the Denver Nuggets, after averaging 14.6 points, 5.6 rebounds, 3.6 assists and 1.0 steal, over 32 games played in the D-League. The next day, he made his NBA debut, in a 121–120 loss to the Brooklyn Nets, recording one rebound in five minutes off the bench. He later signed a second 10-day contract with the Nuggets, on March 14, and a multi-year contract on March 25. At the conclusion of the 2015–16 season, Toupane was named the NBA D-League Most Improved Player. On October 15, 2016, Toupane was waived by the Nuggets.
On October 30, 2016, Toupane was reacquired by the Raptors 905. On February 25, 2017, Toupane signed a 10-day contract with the Milwaukee Bucks. On March 4, 2017, he was waived by the Bucks, and then reacquired by the Raptors 905 later that day.
On April 10, 2017, Toupane signed with the New Orleans Pelicans, for the remainder of the 2016–17 season. On July 25, 2017, he was waived by the Pelicans.
On July 27, 2017, Toupane signed with the Lithuanian club Žalgiris, of the LKL League. His solid defence helped the team in both the Euroleague, where Žalgiris reached the first Final Four in 19 years and finished in 3rd place, and the LKL, where Žalgiris won the 8th consecutive LKL championship. Axel was also one of the best players in the league cup, which Žalgiris also won.
On July 17, 2018, Toupane signed a two-year deal with the Greek team Olympiacos of the EuroLeague. In 45 games played for Olympiacos, he averaged 5.8 points and 1.8 rebounds per game. On April 13, 2019, Toupane parted ways with Olympiacos.
Unicaja (2019–present)
On August 21, 2019, he has signed 1+1 year contract with Unicaja of the Liga ACB.
