The Cubs acquired the No. 74 international bonus money slot while sending slot No. 28 back to the Rockies.
Butler was a first-round pick by the Rockies in 2012. He has a 6.50 ERA across parts of three seasons in the big leagues and a career 3.33 ERA in the minors. All but one of his minor league appearances has been as a starter. Butler turns 26 next month.
Butler was 8-3 with a 4.45 ERA at Triple-A in 2016 and compiled a 7.17 ERA in 17 appearances, including nine starts, for the Rockies.
The 24-year-old Farris was selected in the ninth round of the 2014 draft by the Cubs. He has a career 2.91 ERA in three minor league seasons.
In adding Butler to the 40-man roster, the cubs also designated right-hander Dylan Floro for assignment.