Horn was acquired by the White Sox from the Cubs on Tuesday in exchange for Matthew Thompson, Ken Rosenthal and Sahadev Sharma of The Athletic report.
The trade clears up space on the Cubs' 40-man roster for the signing of Cody Bellinger, which will soon be made official. Horn made 39 relief appearances at Triple-A Iowa last season and had a 4.58 ERA, 1.53 WHIP and 59:29 K:BB across 53 innings.