The Cubs selected Rios' contract from Triple-A Iowa on Sunday.
Rios joined Chicago on a minor-league contract in January and will get a look in the majors after posting a 5.06 ERA, 1.47 WHIP and 8:6 K:BB over 10.2 frames with Iowa to begin the season. The right-hander last pitched in the majors in 2023 and has a 6.23 ERA in 92 career MLB appearances.