Doumit, 30, is a career .271 hitter in seven seasons with the Pittsburgh Pirates.
Doumit is expected to back up Joe Mauer at catcher in Minnesota. He's also expected to spend time at DH and in the corner outfield positions.
His deal, which includes undisclosed performance bonuses, is set pending completion of a physical exam next week.
Doumit spent seven years with the Pittsburgh Pirates, finishing the 2011 season with a .303 average, eight homers and 30 RBIs in 77 games. He missed two months with a severely sprained ankle. His best year was 2008, when he batted .318 with 15 homers and 69 RBIs in 116 games.
Also Friday, the Twins added three prospects to their 40-man major league roster: outfielder Oswaldo Arcia, right-handed pitcher Carlos Gutierrez and left-handed pitcher Tyler Robertson. They removed right-handed pitcher David Bromberg from the 40-man roster and outrighted him to Triple-A Rochester.
Jerry Crasnick is a senior baseball writer for ESPN.com. The Associated Press contributed to this report.