Romo, who turns 30 on March 4, has helped San Francisco's staff join the ranks of the elite. He's 20-9 with a 2.20 ERA in 276 games over five seasons. In that stretch, Romo has struck out 277 and walked just 48 in 233 1/3 innings.
Thrust into the closer's role last year after Brian Wilson sustained an elbow injury and Santiago Casilla was demoted, Romo converted 14 saves in 15 opportunities while finishing 4-2 with a 1.79 ERA in 69 regular-season appearances.
Romo was even more effective in the postseason, allowing one earned run in 10 2/3 innings spanning 10 outings. He totaled four saves, including three in San Francisco's four-game sweep of Detroit in the World Series. Those three saves matched Romo's regular-season career total entering 2012.
Terms of the deal were not announced, though Giants vice president of baseball operations Bobby Evans indicated that it gives the ballclub "cost certainty" while potentially rewarding Romo. Evans cited an "escalator" clause in the first year of the contract that will hike Romo's 2014 salary if he thrives as a full-time closer this season.
Romo, who earned $1.575 million last year, filed for $4.5 million for a one-year salary when teams and players exchanged figures on Jan. 18. The Giants countered with a $2.675 million offer.
San Francisco managed to reach agreements and avoid hearings with all six of its arbitration-eligible players, with the other five being catcher Buster Posey, right fielder Hunter Pence, left-hander Jose Mijares, outfielder Gregor Blanco and infielder Joaquin Arias.
"It's important to go into spring not having that hanging over our heads," Evans said.
Chris Haft is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.