Jimmy Rollins also went deep and Jonathan Papelbon retired pinch-hitter Adam Kennedy on an easy popup with a runner at third to end it. The last-place Phillies have won three straight and get ace Roy Halladay back from the disabled list Tuesday night after missing seven weeks with a lat injury.
Howard, the 2006 NL MVP who averaged 132.7 RBIs over the previous six seasons and led the NL three times with 140 or more, missed Philadelphia's first 84 games because of the ruptured left Achilles tendon he sustained while grounding out to end last year's NL division series against St. Louis. His leadoff homer in the fourth was his first RBI in six games and 18 at-bats since coming off the disabled list.
Blanton (8-8) allowed two runs and six hits, struck out seven and walked none while helping the Phillies win three straight games for the first time since a four-game stretch May 23-26. The right-hander did not give up a home run for the first time since May 8 against the New York Mets, after 11 consecutive starts in which he allowed at least one and 19 overall.
The Dodgers have the second-fewest homers in the majors, just one more than San Francisco.
Papelbon pitched a scoreless ninth for his 20th save in 22 attempts.
Nathan Eovaldi (1-6) allowed three runs and six hits in five innings before he was removed for a pinch-hitter. The 22-year-old right-hander was moved up a day in the rotation along with Chris Capuano because of an injury to Chad Billingsley, scratched from Sunday's start because of inflammation in his right elbow.
Capuano, who was scheduled to start the opener of this three-game series, lost 7-2 to San Diego after the Dodgers made five errors and gave up six unearned runs.
Juan Pierre, who spent three seasons with the Dodgers and was pushed out of a starting role in 2008 after the acquisition of Manny Ramirez, opened the scoring for the Phillies in the second inning with a two-out RBI single.
Rollins made it 2-0 in the third, driving a 3-2 pitch into the left-field pavilion for his ninth homer. Howard, who flied out to the left-field warning track his first time up, homered to left on Eovaldi's first pitch of the fourth to make it 3-0.
The Dodgers had runners at the corners with one out in the bottom half when third baseman Placido Polanco fielded Juan Rivera's grounder and got lead runner Mark Ellis caught in a rundown. Phillies catcher Carlos Ruiz ran him back to third, then made a lunging tag with the ball in his other hand, and third base umpire Mike Winters made the ''safe'' call as Ellis trotted home. But plate ump Bill Miller ruled him out for running outside the baseline trying to avoid Ruiz.
Jerry Hairston Jr. led off the Dodgers' sixth with a double and advanced on a grounder by Ellis that second baseman Chase Utley fielded in the hole before throwing to first. Howard never got the handle on the ball, but first base umpire Wally Bell signaled ''out,'' thinking that Howard had simply dropped the ball after making the transfer from his glove.
Dodgers manager Don Mattingly came out to argue. But before he got to Bell, he was already huddling with the other umpires and the call was reversed. Then Phillies skipper Charlie Manuel came out to argue and got a full explanation before returning to the dugout. Matt Kemp came up and drove in Hairston with a groundout.
Rivera led off the seventh with a single and scored on Blanton's two-out wild pitch.
NOTES: The victory was the Phillies' 900th against the Dodgers during the regular season since the rivalry began back in 1890. The Dodgers have beaten them 1,144 times. They've also met in the postseason five times, with the Dodgers winning NL championship series in 1977 and 1978, and the Phillies winning the NLCS in 1983, 2008 and 2009. ... Blanton is 7-0 with a 2.05 ERA in eight starts this season when pitching seven or more innings. In his other 10 starts, he is 1-8 with a 7.67 ERA. ... Howard needs six extra-base hits for 500 in the majors. ... The Dodgers, who swept a four-game series at Philadelphia during the first week of June, have lost six straight to the Phillies at home.