Prince Fielder hit his first homer since Aug. 13, but slumping Milwaukee lost for the eighth time in 11 games.
Moyer (14-7) allowed three runs and four hits, improving to 7-1 in his last 13 starts. The 45-year-old left-hander moved past Hall of Famer Juan Marichal and into a tie with Jack Powell for 49th on the career list with 244 wins.
Pitching on three days' rest for the first time since 2004, Moyer kept the Brewers off balance with his usual assortment of batting practice-speed fastballs and even slower stuff.
He left after Fielder's two-run shot made it 4-3. Ryan Madson pitched two innings, Chad Durbin retired the only batter he faced with two on in the eighth and Brad Lidge finished for his 36th save in as many chances.
Sheets entered with a 20-inning scoreless streak, but couldn't extend it. The All-Star right-hander allowed five runs and nine hits in six innings.
Howard connected in the first to give the Phillies a 2-0 lead. He launched a first-pitch fastball into the bushes beyond the center-field wall for his fourth homer in six games.
J.J. Hardy sliced the lead in half with a two-out homer in the third, but the Phillies answered with two runs in the fourth. Howard nearly hit another two-run shot, settling for an RBI double when his drive to center bounced off the top of the wall. It was his major league-leading 129th RBI. Pedro Feliz lined a two-out double just over right fielder Cory Hart's head to make it 4-1.
Fielder had gone 67 at-bats without a homer before going deep in the sixth.
Carlos Ruiz had an RBI double in the bottom half to give Philadelphia a two-run cushion. His suicide squeeze in the eighth provided the final margin.
Notes: No non-knuckleball-throwing pitcher 45 years or older has won more games in a season than Moyer, the oldest player in the majors. Moyer is 6-3 in 15 career starts on three days' rest. ... Howard is batting .417 (10-for-24) with 10 RBIs during a six-game hitting streak. ... The Phillies haven't named a starter for Sunday, though Brett Myers is more than willing to pitch on three days' rest. ... The Brewers fell to 31-18 against left-handed starters.