Roma signed the 33 year old Matic as a free agent after his Manchester United contract expired this summer.
Matic, who revealed in April that he would be leaving Manchester United at the end of the season, is reunited with former Manchester United boss Jose Mourinho for a third time.
Matic joins Roma on a one year deal that runs until 30 June 2023. The deal also has the option to extend by an additional year.
The Italian club confirmed the capture of Matic on their official website: “The club is delighted to confirm the signing of Nemanja Matic.
“Matic, 33, has put pen-to-paper on a one-year contract with the Giallorossi that runs until 30 June 2023.”
Matic spent five years at Manchester United after joining from Premier League rivals Chelsea in 2017 for £40million.
Matic said after completing the transfer to Roma: “I am pleased and honoured to be joining this club and I cannot wait to start the new season with my team-mates.
“Roma is a big club, with amazing fans and a coach, Jose Mourinho, who is well known to everyone – making the decision to come here very straightforward.
“I hope that by working together we are able to achieve some great things.”
Roma’s general manager Tiago Pinto added: “Nemanja brings with him to Roma not just a lot of quality on the pitch, but the vast experience he has gained from so many seasons in the Premier League and a focus and mentality that has consistently set him apart throughout his career.”
Matic has a long history with Mourinho, who he played under at both Manchester United and Chelsea.
The midfielder has played 159 times for the Portuguese manager, more than he has played under any other boss.
Mourinho first signed Matic as Chelsea manager in £21m in 2014 before signing the midfielder again as Manchester United boss in 2017.