The Twins on Saturday night announced the deal that netted them Romo, Chris Vallimont, a right-handed starter in High-A, and a player to be named later from the Miami Marlins in exchange for Double-A first baseman Lewin Diaz.
The 36-year-old Romo has spent the season as the Marlins' closer, racking up 17 saves to go along with a 3.58 ERA in 37⅔ innings.
"They're in a really, really good position to make a playoff push. That's exciting. It's super fun baseball to play,'' Romo said after the Marlins' 9-2 loss to Arizona on Saturday night.
"But kind of mixed feelings based on the fact I get to leave a bunch of dudes I've grown to love. Cool dudes who allowed me to be myself."
Romo won three championships with the San Francisco Giants, closing out the final game of the 2012 World Series in memorable fashion when he froze Miguel Cabrera on a down-the-middle fastball. In 23⅓ career playoff innings, Romo has a 3.09 ERA.
He provides a strong right-handed complement to left-hander Taylor Rogers, who has emerged as the Twins' closer and one of the most valuable relievers in the league for first-year manager Rocco Baldelli.
"[Romo's] ultra-competitive, he wants the ball and he's scared of nothing,'' Baldelli said. "I think everyone knows him as a pitcher. He's been around a very long time. He's had a very successful career, he's pitched in some big, big spots, and once you get to know him you can see how he's had success in those spots.''
The Twins have shuffled relievers in and out during the past week, designating veteran Blake Parker for assignment and calling up rookies Cody Stashak and Sean Poppen. The Twins, who at 63-41 hold a one-game lead over the Indians, have cobbled together a middle-of-the-pack bullpen but needed to upgrade it as Wednesday's trade deadline approaches.
"[Romo's] got a lot of experience in the big leagues and he's going to help us a lot. His experience is going to help us,'' Twins pitcher Martin Perez said.
Minnesota is expected to pursue at least one more major league pitcher before the deadline.
The Marlins continue to explore selling some of their cadre of young starting pitching in hopes of improving their future as they barrel toward a 100-loss season. At 39-63, the Marlins are six games behind the next-worst team in the National League (Pittsburgh), and in addition to dealing a starter, they could trade second baseman Starlin Castro.
"We felt like we maximized an expiring asset and were able to add, in our opinion, one of the most productive, impactful power hitters in all of minor league baseball,'' Marlins president of baseball operations Michael Hill said of the Romo deal.
The 22-year-old Diaz was hitting a combined .297 with 19 home runs and 61 RBIs in Class A and Double-A.
The 22-year-old Vallimont was a combined 6-7 with a 3.16 ERA for two Class A teams this season.
Information from The Associated Press was used in this report.