Inter agreed on a permanent contract with fellow Series A side Roma left-back Aleksandar Kolarov for an initial fee of €1.5million.
Kolarov, who also played in the Italian top flight for Lazio, is thought to have signed a one-year contract with the possibility of a second season.
The agreement between Inter and Roma includes numerous possible add-ons worth up to €500,000, depending on various targets being met.
Serbia international Kolarov, 34, made 132 appearances during a three-season spell at the Stadio Olimpico, scoring 19 goals – seven of those coming in the 2019-20 Serie A campaign.
Inter had already strengthened their defence during the close season with the arrival of right wing-back Achraf Hakimi from Real Madrid in a reported €40m deal.
Kolarov, who has 92 international caps, won major honours during a career-defining seven-year stint with Manchester City, claiming two Premier League titles and the FA Cup.
He joins an Inter side that finished second last season, with Antonio Conte’s men kicking off the new campaign at home to Fiorentina this month.