The Brewers, who had lost five straight before playing Pittsburgh this weekend, won for the second consecutive game and are 7-3 this season against the Pirates.
Pittsburgh has lost five straight overall and 23 of 25 on the road. The Pirates have dropped 26 of their last 29 games at Miller Park.
Dave Bush (4-6) pitched 6 1-3 innings for the Brewers, giving up two runs and six hits. It was his fifth straight quality start. Kameron Loe got the last two outs of the seventh for the Brewers and Zach Braddock pitched a scoreless eighth.
John Axford worked the ninth inning, giving up a leadoff homer to Ryan Doumit. Axford got the next three batters to earn his 10th save in 10 chances.
Jeff Karstens (2-4) tossed five innings for the Pirates, giving up four runs and five hits. He walked six and continued to have problems with the home run ball. With the two homers he yielded Saturday, he has given up 16 this season.
Braun has been struggling in recent weeks, but he snapped an 0-for-19 slide and drove in the game-winning run in the 10th inning Friday night. He hammered a slider from Karstens in the third inning to center for his 12th home run of the season. It was his first since June 28 against Houston.
Fielder followed with a mammoth drive to right-center for his 20th home run this year and second in two games to give the Brewers a 3-0 lead.
Craig Counsell's sacrifice fly in the fifth made it 4-0.
Garrett Jones hit his 11th home run in the sixth and Andrew McCutchen's sacrifice fly in the seventh cut the lead to 4-2.
The Brewers went up 1-0 in the first. After striking out the first two hitters, Karstens walked Braun and Fielder. Casey McGehee singled to left field to score Braun.
NOTES: Brewers rookie catcher Jonathan Lucroy was out of the lineup again with a sore right hand. Lucroy will also miss Sunday's game, but is expected to return after the All-Star break. ... The Brewers and Pirates celebrated Cerveceros, with the Brewers wearing blue "Cerveceros" uniforms and the Pirates donning gray "Piratas" uniforms. ... Pirates pitcher Sean Gallagher hit Rickie Weeks in the back with a pitch in the sixth, prompting a warning to both benches from plate umpire Bob Davidson. The teams have a history of beanballs the last few seasons.