[3][4] Emil Nielsen started playing handball at the age of 10 and made his debut for Aarhus Håndbold at 17.

[6] Despite his health challenges, Nielsen attracted interest from Danish club Skjern Håndbold, who signed him even though he was unable to participate at the start of the season.

[8] In 2019, he signed a three-year contract with the French LNH Division 1 club HBC Nantes, which, according to TV 2 Denmark, paid a transfer fee of approximately DKK 1 million.

[12] Nielsen ended up starring in the final, being named player of the match, though he was unable to secure victory, as Denmark lost to France in extra time.

[14] During the 2024 Summer Olympics, Nielsen's father died, but he stayed in Paris and continued to compete, contributing to Denmark's gold medal victory.