Ronaldo is set to join the Serie A champions, after they agreed a stunning €112million deal with Real Madrid on Tuesday.
The 33-year-old will sign a four-year deal, taking him to when he is 37.
Mendes, speaking with Sport, says he expects Juve to be his final club.
“I’m very happy for Cristiano.
“Juventus will be his last club and I’m glad he made this decision. With this team he’ll close out his marvellous career.
“I thank [President] Andrea Agnelli in particular for his determination and his willingness to negotiate with Real Madrid, and I also thank [general manager] Beppe Marotta for his professionalism,” he said.