The deal is worth $4.25 million and includes a club option for $6.5 million, with a buyout of $500,000, sources said.
"There were other talks with other teams but they didn't go real far," Maholm said. "With the talks with (Cubs general manager) Jed (Hoyer) it wasn't a clear-cut deal when we started, but it was something I wanted. After the new year I said to my agent, that's the place and to get it done."
Maholm made $6.25 million in 2011, the final year of the $13.75 million deal he signed with the Pirates before the 2009 season. He was the Pirates' No. 1 draft pick in 2003 and was a combined 53-73 with a 4.36 ERA in seven seasons in Pittsburgh.
Maholm, 29, was shut down at the end of last season because of a left shoulder injury.
"It was a pulled muscle," Maholm said. "It wasn't anything huge. The timing of it when it happened was the reason I missed the end of the season. I just wanted to make sure that I was healthy and that I didn't do anything further to my shoulder. I went to Dr. (James) Andrews' physical therapy guys once a week and got some exercises. I rested, and I have now been working out and long-tossing. I should be starting bullpens next week."
Although Maholm was 6-14 in 2011, he posted a respectable 3.66 ERA, the lowest of his career for a full season. Maholm is a sinkerball pitcher who has allowed less than one home run per nine innings pitched in his career. He's given up an average of 13 home runs per season over the last three years. Those numbers indicated to the Cubs' front office that he can be a valuable arm in Wrigley Field, a ballpark that can be home-run friendly depending on weather conditions.
"Maholm is a ground ball pitcher and (newly acquired pitcher Chris) Volstad is a ground ball pitcher so that's important," Hoyer said. "It's important to have a mixture on your staff. You don't want a staff of all ground ball guys or all fly ball guys. You want to have pretty good diversity."
Hoyer said the addition of a sixth starter doesn't necessarily mean a rumored trade of Garza is on the horizon.
"As a rule of thumb, we aren't going to comment on trade discussions," Hoyer said. "I would say with this Maholm contract and the fact that we have six starters right now is not a precursor to anything. I'm not going to comment on trade rumors, but it's important to note that [signing Maholm] isn't a precursor deal."
The addition of Maholm gives the Cubs another left-hander for the starting rotation. The Cubs, who acquired Wood from the Cincinnati Reds last month, have been searching for reliable starting left-handed pitching since trading Ted Lilly to the Los Angeles Dodgers in July 2010.
"I think we are very comfortable with the names we have," Hoyer said of the Cubs' rotation. "You never know what is going to happen over the course of the winter and what is going to be available to us. But what we said was that a huge priority was building depth. We feel like we've really done that.
"But the minute you feel you have enough pitching, you don't. We are happy with the depth we built up over the winter, but it's a dangerous thing to say you are ever done."
Maholm falls into the group of players that president of baseball operations Theo Epstein and Hoyer have identified who did not have strong seasons in 2011 and are projected to bounce back.
Bruce Levine covers the Cubs for ESPNChicago.com and ESPN 1000.