The right-hander now has won a career-high six straight decisions, and he has a 0.95 ERA since the All-Star break, which leads the Major Leagues. Teammate Kyle Hendricks is second with a 1.31 ERA.
Hammel has not given up a run in his last 22 innings, all at Wrigley Field.
"He was really, really good again and it was fun to watch," Cubs manager Joe Maddon said.
"I'm just going out by out," Hammel said. "I had good fastball command except for three or four hitters. The walks are bugging me. I could do without the walks -- unnecessary stress with those walks. If I could clean those up, we'd be in a good place."
Hammel walked three and gave up two his while striking out seven over seven innings. Does he remember the last time he gave up a run?
"I know the last few [starts] have been real good," Hammel said. "It's a different chess match each time you go out."
For the record, the last run was July 27 when White Sox pitcher Anthony Ranaudo led off the fifth with a home run.
Hammel is part of a good trend for the Cubs. Chicago's starting pitchers are 10-0 with a 1.12 ERA in 14 games this month, and the rotation has given up two or fewer runs in 11 straight games. And Hammel is the fourth starter.
For a pitcher who has struggled in the second half in the past, he's on a good roll.
"He was throwing strike one, being aggressive," Chicago catcher David Ross said. "[The Brewers are] a better lineup than people give them credit for.
Carrie Muskat has covered the Cubs since 1987, and for MLB.com since 2001. She writes a blog, Muskat Ramblings. You can follow her on Twitter @CarrieMuskat and listen to her podcast. This story was not subject to the approval of Major League Baseball or its clubs.