Tyler Clippard, traded out of a pennant race last month, is headed to a contender.
The White Sox had picked up Clippard from the New York Yankees as part of a seven-player deal on July 18.
Clippard, 32, is 2-6 with three saves and a 4.27 ERA in 51 combined appearances this season between the Yankees and the White Sox.
Since the All-Star break, Clippard has a 1.50 ERA in 13 appearances.
He is a free agent at the end of this season, and he is owed approximately $1.2 million for the rest of the season.
The Astros need help in their bullpen, as their relievers came into Sunday ranked last in the American League since the All-Star break in ERA, at 5.45.
In his 11 major league seasons, Clippard has a 48-41 record with a 3.04 ERA, 59 saves and 738 strikeouts in 609 career appearances, including eight starts.
The Astros will make a corresponding roster move on Monday, when Clippard is expected to join the team for the series opener at Arizona.
To fill their vacant roster spot, the White Sox will make a corresponding move prior to their Tuesday game against the Dodgers in Los Angeles.