With the Phillies leading 2-0 in the fourth, Howard sent the first pitch he saw from Nathan Eovaldi (1-6) into the left-field bleachers for a solo shot -- his first homer since Oct. 1, 2011, in the first-round playoffs against the St. Louis Cardinals.
Howard ruptured his Achilles tendon four games later and didn't return to action until July 6.
Jimmie Rollins also went deep for the Phillies, who took the first of a three-game set.
Joe Blanton (8-8) held the Dodgers to two runs on six hits over eight innings. The right-hander didn't issue a walk and fanned seven en route to the victory.
Jonathan Papelbon picked up his 20th save for the Phils.
Eovaldi was touched for three runs on six hits over five innings.
The second-place Dodgers fell two games behind idle San Francisco in the National League West with their sixth loss in seven contests.