The Cubs later dealt reliever Carlos Marmol and international signing bonus slot No. 4 to the Los Angeles Dodgers for reliever Matt Guerrier. Chicago also dealt minor league infielder Ronald Torreyes to the Houston Astros for their second and third international signing bonus slots.
Despite inconsistent starting pitching this season, the Orioles entered Tuesday with a 47-36 record. Baltimore's starting pitchers have posted a 4.79 ERA this season, the third-highest mark in the American League.
Feldman, 30, is 7-6 with a 3.46 ERA in 15 starts this season with the Cubs. Prior to signing with the Cubs this past offseason, the right-hander spent the previous eight years with the Texas Rangers and was a 17-game winner in 2009.
"It's never easy to give up a guy that's performed for you but I think the chance to add two power arms was very important to us and we're excited to have both guys," Cubs general manager Jed Hoyer said.
Feldman was scheduled to start for the Cubs against the Oakland Athletics on Tuesday night. Left-hander Chris Rusin will make the start instead. Hoyer said Carlos Villanueva, who started the season in the rotation, will be stretched out and might eventually end up taking Feldman's spot.
Strop, 28, has struggled this season, going 0-3 with a 7.25 ERA in 29 relief appearances. The hard-throwing right-hander was Baltimore's primary setup man last season, when he posted a 2.44 ERA in 70 games.
Once considered a top prospect, the 27-year-old Arrieta went 1-2 with a 7.23 ERA in five starts this season. The right-hander owns a 5.46 ERA in 69 games -- 63 starts -- over parts of four seasons with Baltimore.
"We're very excited about the players we got in return," Hoyer said. "Both guys have good arms. When you look at Arrieta, he's a guy who struggled recently in the big leagues but we see a lot of potential in him. We've had some luck with guys like Travis Wood coming off a down year, Feldman was coming off [a down year with the Rangers].
"We think Arrieta, getting him out of the American League East and getting him into our environment, we're hopeful he can turn the corner. This is a guy who was an Opening Day starter for the Orioles in 2012 and we hope to get him back to that level of performance."
ESPN MLB Insider Keith Law contributed to this report.