Theo, who previously went by the artist name Theoz, will perform in Sunday's fourth qualifying round of "Hello Mello".
The guest artist will perform a "supermedley" about the journey from young debutant to the artist he is today.
"I'm really looking forward to performing on stage and meeting all the contestants in 'Hello Mello'", says Theo in a press release.
Theo competed in Melodifestivalen in 2022 and 2023 and made it to the final both times.
"Hello Mello" is SVT's music festival for artists between 13 and 15 years old. A total of 25 young artists will compete in five qualifying rounds and the winner of the final will get to perform in the "big" Melodifestivalen next year.
