As a youth player, Sander played for a local clubs, before joining AaB in 2017 at the age of 12.[3] Possessing a physique suited for the goalkeeping position, Sander impressed in various youth teams and attracted interest from some of Europe's major clubs. In January 2021, AaB confirmed that Sander had been on a trial with Italian giants Juventus. AaB stated that they were "in dialogue with several clubs about Theo Sander".[3] He would, however, end up staying at AaB. In April 2021, Sander was called up for his first professional game against Vejle Boldklub. However, he remained on the bench. In the 2021–22 season, Sander was on the bench for 14 Danish Superliga games.
In February 2022 AaB confirmed, that Sander had signed a new deal until June 2025.[4] On 28 August 2022, 17-year old Sander made his official debut for AaB against Randers FC in the Superliga.[5] AaB lost the match 1–0 after a bad pass from Sander was intercepted by Filip Bundgaard.[6] With his debut, Sander became the youngest goalkeeper in the Danish Superliga history.[7]
Copenhagen
On 20 July 2023, after AaB suffered relegation to the second division, Sander joined Copenhagen, on a deal until June 2028.[8] He made his competitive debut for the club on 18 August, replacing an injured Kamil Grabara as starter in goal, keeping a clean sheet in a 2–0 victory against Hvidovre.[9][10] In December 2023, Sander received surgery after suffering a knee injury, which kept him out for several months.[11]
Personal life
Born in Denmark, Sander is of French and Danish descent.[1]
^Egelund, Klaus (28 August 2022). "Debutmareridt i AaB-nedtur". Ekstra-Bladet (in Danish). Archived from the original on 5 September 2022. Retrieved 31 October 2022.