Marquis, 33, posted a 4.43 ERA in 23 starts with the Nationals and D-backs last season. He also struck out 76, walked 43 and allowed 11 homers in 132 innings.
"As everybody is aware, we're looking for pitching, starting pitching in particular, and Jason fits that bill," Twins general manager Terry Ryan said. "He's a ground-ball machine and he throws the ball over the plate. I think our ballpark will suit our needs and his. Obviously, we have to support him defensively, but he's a guy who has taken the ball and has hundreds of starts and veteran experience. We're glad to have him here."
Marquis brings plenty of experience, as he has a career 4.55 ERA in 12 seasons with the Braves, Cardinals, Cubs, Rockies, Nationals and D-backs.
This will mark his first season in the American League, but Marquis said he's looking forward to the challenge and the ACES client told his agents at the beginning of the offseason that he had interest in the Twins.
"I'm very excited to be able to contribute, and this sounds funny to me, but to an AL Central Division crown," Marquis said. "I'm hoping I can bring some leadership on and off the field. But you don't win this on paper. You have to go out there and play it and see what happens."
Marquis has historically been an innings eater, as he made at least 28 starts every year from 2004-09. But he made just 13 starts with the Nationals in '10 because he had surgery to remove bone chips from his right elbow.
And last season, he made 23 starts, including just three with the D-backs because his season was cut short when he suffered a fractured right fibula after being struck by a line drive on Aug. 16. But Marquis tried to remain in that game even after breaking his fibula, and said he brings that intensity to every start.
"I don't know any other way really," Marquis said. "My job is to take the ball every five days and go as deep as I can into the game and try to win. I pride myself on that, and on my competitiveness and toughness."
Marquis fills a need as a back-of-the-rotation starter, as left-hander Brian Duensing remains a likely candidate to be moved to the bullpen next season.
Ryan, however, said it's not set in stone that Duensing will become a reliever, but added that Scott Baker and Nick Blackburn are expected to be fully healthy in time for Spring Training. He also said that Francisco Liriano will not pitch in the Dominican Winter League, as he's throwing at the club's academy there instead to limit his innings.
But Ryan said the club is still hoping to add pitching this offseason, as the bullpen finished with the worst ERA in the Majors and Twins starters combined to post the third-worst ERA in the American League last season (4.64) while striking out just 617 batters in 961 innings.
"I think we are still on the lookout for it," Ryan said. "I don't know that any organization has the roster set the way they want. But this helps us in a few ways. It gives us a veteran starter in our rotation and some depth to help us if we have injuries."