"He's not a rookie any more," Howard said. "He's proven himself to be a very poised pitcher."
Philadelphia, which has won five of six, dropped the third-place Braves six games back in the National League East and left Atlanta in a fourth-place tie with Chicago in the NL wild-card race.
After his solo shot made it 1-0 in the second, Howard put the Phillies up 4-1 with his 30th homer in the sixth off Javier Vazquez (10-8).
"I'm just trying to see the ball," said Howard, who has driven in a run for seven straight games, with 12 RBIs over that span. "I got some good swings tonight and fortunately for us, they got on the other side of the fence."
Howard's multihomer game was his third this season and the 20th of his career, tying the slugger for third place on Philadelphia's career list with Dick Allen.
The Braves had won the last seven starts made by Vazquez, who allowed six hits, four runs and two walks in seven innings with seven strikeouts. Howard proved too tough, particularly when Vazquez left a change-up too high in the strike zone in the sixth to the All-Star first baseman.
"He's got 30 home runs for a reason," Vazquez said. "He's a powerful guy and you've got to be careful with him."
The start of the game was delayed 1 hour, 37 minutes by rain. When it finally got going, Happ and Vazquez were in control.
Happ (9-2) surrendered three hits, including Matt Diaz's seventh homer in the fourth. The 26-year-old left-hander gave up one run, six walks and struck out three in 7 2/3 innings. He lowered his ERA to 2.66 and become a solid member of the Phillies' rotation.
Striking out Yunel Escobar to end the first with runners on second and third boosted Happ's confidence.
"I was lucky to get out of the first inning," Happ said. "You get behind in the first, you know you have to battle all the way. I was really anxious during that inning."
Atlanta, which had just two runners in scoring position after the first, left the bases loaded in the sixth when Happ got Ryan Church to foul out.
"He's got that late life on the fastball that makes that fastball up look good," Diaz said of Happ. "The minute you start cheating on that late life on that fastball, it makes his off-speed pitches look good."
Ryan Madson relieved Happ for the final out of the eighth. One night after Lidge blew a save for the eighth time this season, Phillies manager Charlie Manuel brought in lefty Scott Eyre to begin the ninth with left-handed hitters coming up.
The Phillies improved to 37-20 on the road, best in the majors. They are 11-5 in their last 16 games away from Citizens Bank Park.
"In the second week of August, you're about to get in the homestretch, and you need to be able to handle your division games," said Howard, whose team improved to 20-7 this season when he homers. "We left (Saturday's loss) in the past."
Braves 2B Martin Prado walked as a pinch-hitter in the seventh. He was scratched from the lineup because he still felt dizzy from heat-related problems that forced him to leave Atlanta's 4-3 win Saturday. ... LF Garret Anderson, who went 0 for 3, batted second in the order for the first time in 85 games with Atlanta. ... Phillies RHP Brett Myers has been cleared by an ophthalmologist for a long-toss session on Monday, three days after injuring his eye.