Valdifiori made a permanent transfer with Nikol Maksimovic on loan for €5m and obligation to buy at €20m.
“As I made clear to my manager over the last few weeks, I was only prepared to leave Napoli for Toro," said Valdifiori.
“It is precisely what happened, so I am very happy. I thank President Cairo and director Petrachi for the tenacity with which they wanted to bring me to Toro.
“I am very fired up, impatient to start this new exciting adventure."
President Urbano Cairo also commented on the official club website.
“When our Coach Sinisa Mihajlovic told us that we needed to sign a midfielder who could control the tempo and dictate the passing, our objective immediately became Valdifiori.
“He was always our first choice, so on behalf of the whole club, with great pleasure I welcome Valdifiori to Torino."