After representing his country in the World Cup in Russia this summer, the 33-year-old had free time to recover properly for the new season.
And the five-time winner of the Golden Ball will wear the white and black striped shirt of the Old Lady for the first time.
Juve is playing in his traditional pre-season friendly against Team B in Villar Perosa.
The city, located on the outskirts of Turin, is the home of the Agnelli family that owns the club and will host the friendlies that take place every year since 1955.
"Since I was a child, I looked at this team and said I hope to play there someday."
Every year there are thousands who flock to attend the game, but this time the CR7 effect has been in line since the first hours of the morning.
There are only 5,000 tickets available, but it is believed that there are around 15,000 in the area to see the main team face the youth team.
Less than a week before the opening match of Serie A against Chievo, Max Allegri uses a 4-3-3 formation with Ronaldo in the role of central forward flanked by Paulo Dybala and Douglas Costa.
The new signing, Emre Can also starts in midfield, with Leonardo Bonucci returning to the center after his brief stint in Milan.
The match starts at 4pm, UK time.
Since moving to Italy, Ronaldo says he dreamed of playing for Juve since he was a child.
"I feel great, everything is fine, the test was good, the people around the stadium, the fans, the people in the training camp are very kind to me, I'm happy, I'm happy," he told Juventus TV.
"Great club, first of all it's a great club, since I was a kid, I looked at this team and said I hope to play there someday, now I'm going to play in a fantastic club, one of the biggest in the world. .
"I do not have a precise moment when I decided." Over the years, we played sometimes against Juve and I had the special feeling that Italian fans like Cristiano.
"It's the biggest club in Italy, one of the best in the world, so it was an easy decision, since Juve is an incredible club."
Juventus: Szczesny; Square, Bonucci, Chiellini, Alex Sandro; Bernardeschi, Bentancur, Can; Douglas Costa, Cristiano Ronaldo, Dybala
Banco Juventus: Pinsoglio, Perin, Pjanic, Khedira, Marchisio, Matuidi, Barzagli, Mandzukic, Joao Cancelo, Rugani, Beruatto, Fagioli