Duensing, who turns 34 in February, posted a 4.05 ERA in 14 games for the Orioles in 2016. He began the year in the Royals organization before being released in May, and missed time with Baltimore due to an elbow injury.
Duensing is 42-37 with a 4.13 ERA in 368 games (61 starts) in eight Major League seasons with the Twins and Orioles. He joins Rob Zastryzny and Gerardo Concepcion as the lone lefty relievers on the Cubs' 40-man roster, with Mike Montgomery expected to join the rotation.
Cash Kruth is a reporter for MLB.com. Follow him on Twitter at @cashkruth. This story was not subject to the approval of Major League Baseball or its clubs.