Matuidi and Juventus mutually agreed to end their three-year association on Wednesday despite the Frenchman still having one year left on his contract in Turin, where he moved from Paris Saint Germain in the summer of 2017, and won three Italian Serie A titles, one Coppa Italia and one Supercoppa Italiana.
The 33-year-old made 133 appearances in all competitions for Juventus and scored eight goals.
Inter Miami are co-owned by former England captain David Beckham, who is a former teammate of Matuidi at Paris Saint Germain.
Miami are currently in their debut season in the MLS but lost their opening two games before the season was suspended because of the coronavirus pandemic.
Confirming the move on Twitter, Matuidi wrote: "I made my decision a few weeks ago to join @intermiamicf, rise to my friend David Beckham's challenge and win new trophies there. My family and I can't wait."
The former Saint Etienne midfielder was an integral part of the France side that won the FIFA World Cup in 2018.
Beckham said: "I couldn't be happier to welcome my friend Blaise to Inter Miami. He is an exciting and gifted player and a great person.
"To have a World Cup winner of Blaise's quality in our new team is such a proud moment - for us as owners and for our fans.
"For me personally, to have a former team-mate joining our club is very special and I can't wait to welcome him and his beautiful family to South Florida."
