Raul Ibanez also went deep for the Phillies, who won despite losing ace Hamels early for the second consecutive start. The left-hander came out in the fifth inning after spraining his left ankle trying to field John Lannan's bunt.
X-rays on Hamels' ankle were negative and the pitcher said he was planning to make his next start, although it will depend on how he responds to treatment.
"There's some frustration, almost comedy," said Hamels, who missed a chance to earn his first victory, but lowered his ERA to 7.27. "Last time I felt like I was doing really well. This time I felt like I was finally getting in a good grove again. I don't know what else to do but laugh about it."
Hamels allowed four hits and struck out four in 4 1/3 innings, leaving with a 5-0 lead.
"It didn't look that good, hopefully it's not too bad," Utley said about Hamels' injury.
The World Series MVP left his start last Thursday against Milwaukee with a bruised left shoulder after being hit by Prince Fielder's line drive with one out in the fourth.
Chad Durbin (1-0) came on in relief of Hamels and allowed only Adam Dunn's sixth-inning homer in 3 2/3 innings.
"Durbin was a key in the game," Nationals manager Manny Acta said. "He shut us down. We couldn't take advantage after Hamels went out."
Durbin got plenty of help from the Phillies offense. Utley had three hits and Ibanez led off the eighth with a home run to left-center, his seventh this season. He also had a go-ahead grand slam in the eighth inning Monday night in a 13-11 victory.
"We have a lot of good hitters from top to bottom," Utley said. "We can swing the bats pretty well."
The fast-starting Utley upped his average to .357 with seven home runs and 20 RBI in 19 games.
"Utley's definitely swinging the bat real good," Phillies manager Charlie Manuel said.
Ryan Zimmerman extended his major league-leading hitting streak to 17 games with a first-inning double off the left-field wall for Washington (4-15), which has lost five of six and owns baseball's worst record.
Zimmerman's streak is the longest for the Nationals organization but trails the franchise record of 31 set in 1999 by Vladimir Guerrero with the Montreal Expos.
The Phillies scored five times in the third on a two-run homer to right by Utley and Feliz's shot to left. Utley led off the fifth with a solo drive to right, giving Philadelphia a 6-0 advantage.
Utley is 8-for-14 with five RBI off Lannan (0-3), who gave up six runs -- three earned -- and nine hits in five innings.
"He made a lot of mistakes in the strike zone, especially with Utley," Acta said of Lannan. "We're scoring enough runs most nights. It's a matter of putting things together."
- Acta said before the game Joel Hanrahan no longer will be the team's closer. Instead, he'll rely on veterans such as Kip Wells and Julian Tavarez in a closer-by-committee, basing who pitches on matchups.
- Washington's Nick Johnson went 0-for-4, snapping his 11-game hitting streak.
- Jesus Flores is 1-for-14 with eight strikeouts against Hamels.