The 18-year-old full-back will move to the Stadio Olimpico from Corinthians on a one-year loan deal which could be made permanent at the end of the season
Zdenek Zeman has been active in the transfer market this summer, bringing in the 18-year-old's compatriots Dodo and Leandro Castan earlier in the window.
Should the player feature for over 45 minutes in at least eight official matches this season, the Giallorossi will have the right to buy him for a €3 million (£2.4m).
Marquinhos has been with Corinthians since 2002, yet made made only six appearances for the Timao first team in the Brasileiro last season.
The Copa Libertadores winner has also captained his national side at Under-17 level and was a reserve for his national side at the London 2012 Olympics.
Marquinhos has a familiar face at the Stadio Olimpico in the form of former team-mate Castan, who was one of Roma’s earlier summer signings.
Roma begin their Serie A campaign on Sunday when they entertain Catania.