The veteran Frenchman run the hosts rugged as he was instrumental in the build-up that resulted in the visitors’ first penalty, scored one goal and was also at the centre of Mateo Musacchio’s sending off.
Ribery’s performance was so good that he was given a standing ovation by a section of the AC Milan supporters when he was substituted in the 88th minute.
Ribery joined Fiorentina on a free transfer in the summer after a 12-year career at German giants Bayern Munich, where he won nine Bundesliga titles and the UEFA Champions League.
Speaking after the game, Ribery expressed delight with the win and banished any lingering doubts of his abilities because of his advancing years.
"I am happy, when you play at San Siro, it's always special. It's a huge arena, so many fans," he told Sky Sport Italia.
"It's a bit difficult for Milan fans right now, but we put in a good performance and that's important for us.
"Yes, I am old, but I feel young on the pitch. Football is my life, I love it. I was hungry when I came to Fiorentina and it excites me to see the team doing so well.
"I came to help Fiorentina, the players and the fans. I am happy, but I need to work every day, every week to play the way I did tonight."
Ribery has appeared six times in the Serie A this season and the former Olympique Marseille winger has registered two goals and an assist thus far.
