The Bosox will receive 25-year-old righthander Zach Stewart and utility player Brent Lillibridge in exchange for the 33-year-old Youkilis, a three-time all-star with a career .287 average.
The White Sox will also picked up $5.5 million of the $6.6 million left on his 2012 contract, and would be responsible for a $1 million buyout on a $13 million team option for 2013, The Boston Globe reported.
"We just thought at this time it was necessary and necessary to do it sooner rather than later," White Sox General Manager Ken Williams told MLB.com. "I just got off the phone with him. He's very excited to join our club. He has a little edge to him which I like."
Youkilis is batting .233 this season with 15 RBI after spending much of May on the shelf with a back strain.
Stewart, 25, has compiled a 3-8 record with a 5.92 ERA in 31 career appearances. Lillibridge, 28, is a career .215 hitter.