Mandragora ended his loan spell at Udinese before joining the Granata.
“It was not difficult to chose Torino. We are talking about an ambitious club with a great history," the 23-year-old said.
“It was easy to choose Torino. I know many players of this group. I've played with Izzo, I know Baselli, Sirigu, Belotti, Zaza, I'll be happy to know the others, I am looking forward to beginning.
“I feel well, the injury belongs to the past, I hope I can help the team with my qualities.