De Decker crashed into the back of a car in Lier, Belgium, last Wednesday and was taken to the local hospital for emergency surgery.

He was later moved to the Antwerp University Hospital.

His team Lotto Dstny announced his death in a statement.

"It is with great sadness that we have to announce the passing of our rider Tijl De Decker," a Lotto Dstny statement read. 

"Today Tijl has lost his battle to recover from the severe injuries he sustained after his crash on training last Wednesday."

"Despite the best efforts of the staff at the hospital, Tijl couldn’t make it through and this morning he lost his battle."

De Decker had won the 2023 Paris Roubaix Espoirs race for U23 riders.

He had signed with Lotto Dstny and was part of their development squad.

The team had announced that he would turn professional in 2024.

"We are devastated by the loss of our cyclist. Tijl showed big progression this year and we believed in his growth margin, stepping up to the pro team was a logical choice," Lotto Dstny chief executive Stéphane Heulot said.

"Unfortunately he will never turn pro and we will always remember him as a talented young rider and a warm and friendly person off the bike."