The Scotland international left Southampton at the end of last season when his contract ended, and has signed a three-year deal with the Italian club.
"Ciao Toro fans. I'm so happy to be here, I can't wait to get started and see you soon," Adams said in a video posted by Torino on social media platform X.
Adams spent five seasons at Southampton, scoring 48 goals in 191 games, and his last appearance came in the Championship playoff final, when he came off the bench as the Saints beat Leeds United to win promotion back to the Premier League.
He made his debut for Scotland in 2021, having earlier played with England Under-20s, and played in all six games for Scotland across Euro 2020 and 2024.
Torino finished ninth in the standings last season, but they struggled for goals scoring 36 in their 38 league games.