The midfielder is a free agent after June 30, because he failed to agree a new deal with Roma.
It is reported the salary he agreed with Inter will be worth an initial €3.3m per season net plus performance-related bonuses, so with add-ons should reach €4.2m per year.
The Armenia international should be tied to the club until June 2024.
However, there is also a clause allowing Inter to terminate after 12 months if Mkhitaryan does not make the minimum number of appearances in the debut season.
The 33-year-old has been in Serie A since 2019, when leaving Arsenal for Roma initially on loan for €3.1m and then as a free transfer.
He made 44 competitive appearances for the Giallorossi this season, contributing five goals and nine assists.
Mkhitaryan limped off with an injury during the Europa Conference League Final against Feyenoord.
— Alessandro De Felice (@aledefelice24) June 21, 2022