Baltimore executive vice president of baseball operations Dan Duquette believes Feldman will stabilize their pitching rotation.
"He's a proven veteran starting pitcher, and he should help stabilize our rotation in the second half of the season."
The Baltimore Sun notes Arrieta was the team's Opening Day starter a season ago. He was 1-2 with a 7.23 ERA in 2013.
Arrieta will be sent down to Triple-A Iowa to make him feel acclimated, per Cubs general manager Jed Hoyer.
"We feel like getting him acclimated, we'll start him off there, and from that point I'm not sure (of) a time frame or what happens. Kind of get him comfortable and have him pitching in the same environment that he was pitching in Baltimore."