The Cardinals scored three times in the first inning. Lohse and two relievers held off the Cubs the rest of the way to give St. Louis its second win in seven games.
Lohse (10-2) scattered six hits with a walk and four strikeouts. He has won his last four decisions.
Jason Motte worked a 1-2-3 ninth for his 21st save.
The Cardinals sent seven men to the plate in the first inning against Ryan Dempster (5-4). Consecutive one-out singles by Allen Craig, Matt Holliday, Carlos Beltran and Yadier Molina accounted for two runs and Lance Berkman drove in a third with a groundout.
Chicago had won two straight and seven out of nine.