The deal is pending a physical. No further details were available.
Kim, a 29-year-old right-hander from South Korea, spent 2007 with the Colorado Rockies, Arizona Diamondbacks and Florida Marlins, going 10-8 with a 6.08 ERA in 28 appearances, including 22 starts.
General manager Neal Huntington said the team's interest in Kim is solely as a reliever. The Pirates entered spring training with their starting rotation set but with four openings in the bullpen.
Also Wednesday, the team had its first full-squad workout under manager John Russell, a three-hour session. In the morning, Huntington and Russell addressed the players.
"I think we're a complete ballclub, and I told the players that," Russell said. "We're not so much the power-hitting team that's going to hit a bunch of home runs, but we can handle the bat, we can pitch, we can play defense. It's a matter of putting it all together."
Although the Pirates are coming off a 68-94 season and did little more than tinker with the roster in the offseason -- Kim's signing will be only their second of a major league free agent -- several veteran players sounded optimistic.
"I think it can be a good team," said shortstop Jack Wilson, the team's most tenured player entering his eighth season in Pittsburgh. "But we all have a job to do, and we didn't do it last year. You're not going to win when, out of 25 guys, maybe three have a good year. How many guys had a decent year? Or even an average year? We all struggled."
First baseman Adam LaRoche said: "It's up to all of us as players to get on board with the program."
Players who missed the workout: second baseman Freddy Sanchez (shoulder), who stayed out of infield drills, and reliever Damaso Marte (flu), who did his first light throwing of the spring.