Fielder's three-run shot off Kyle Kendrick (9-8) made him the second Brewer in team history with four straight 30-plus home run seasons. He helped the Brewers end their six-game road trip on a high after dropping the first five in Cincinnati and Philadelphia.
John Axford tossed two scoreless innings for his 20th save. Carlos Ruiz had two RBIs for the NL wild-card leading Phillies, who ended a five-game winning streak.
Kendrick continues to struggle and could be dropped from the rotation. He's allowed at least four runs in five of his last six starts - bloated numbers that stand out in a rotation anchored by Roy Halladay, Roy Oswalt and Cole Hamels.
The Phillies missed a chance to move into a tie for first in the NL East with Atlanta's loss to Florida. The Marlins are here for a day-night doubleheader on Monday and the Braves play Pittsburgh.
Manager Charlie Manuel said he's only thinking about winning the division and wants his players focused on that fourth straight NL East title.
Kendrick continued to hinder their chances to move into first. He allowed seven hits and five runs in four innings, and ran into trouble from the second batter of the game.
With one out, he allowed a single and a double. Fielder then crushed it into the second deck above a beer ad for No. 30. Only Jeremy Burnitz (1998-2001) ever hit at least 30 homers in four consecutive seasons for the Brewers.
Corey Hart, who homered twice off Halladay on Saturday, doubled in the third for a 4-2 lead. Rickie Weeks' RBI single in the fifth gave Milwaukee seven hits off Kendrick and made it 5-2. Weeks had three hits.
Kendrick heard sarcastic cheers on strikes from Phillies fans more used to gems tossed by their top three starters.
Triple-A pitchers Nate Robertson and Vance Worley are with the team and are expected to be activated in time for Monday's doubleheader. Oswalt pitches one of the games, and Robertson or Worley will pitch the other. Perhaps a strong outing from one of the call-ups would be enough for Manuel to consider skipping Kendrick the next time around.
Wolf, a former Phillie with a "Wolf Pack" fan club in the upper deck, struck out five and allowed two runs in 6 2-3 innings to win for the first time since Aug. 18. Wolf (11-10) only ran into trouble in the second when Ruiz poked a double to left that cut the lead to 3-2.
Axford retired Ben Francisco on a flyball with two on in the eighth to snuff Philadelphia's late-inning rally. The Brewers tacked on an unearned run in the ninth.
NOTES: Phillies RHP Scott Mathieson was scoreless in 1-plus innings. He worked with minor league pitching consultant, and Hall of Fame closer, Bruce Sutter on the split-finger fastball the last few weeks in the minors. Mathieson said he planned to work with Sutter in the offseason and hopes it's the pitch that will keep him in the majors. ... Robertson is with his fourth organization this year. He received a big, extended hug from former Tigers teammate Placido Polanco before the game. ... Wolf fanned his 1,500th career batter. ... Werth threw out Hart at the plate in the ninth.