Buehrle (12-7), who was 0-4 in his last eight starts, allowed one run on eight hits and two walks in seven-plus innings.
Mark Kotsay had two hits and two RBI and Carlos Quentin had a two-run homer, as Chicago won for the fifth time in six games.
Kevin Youkilis drove in Boston's only run.
Josh Beckett (14-6) remained winless in his last five starts, allowing three runs on six hits and two walks in seven innings.
The loss dropped the Red Sox to 8 1/2 games behind the New York Yankees in the AL East. Boston leads Texas by 2 1/2 games in the AL wild-card chase.
Copyright 2009 by United Press International.