Arenado and Gonzalez hit back-to-back homers in the first inning, backing a sharp outing by Jorge De La Rosa, and the Rockies beat struggling San Francisco 2-1 on Friday night to send the Giants to their seventh straight loss.
"They're hot. They won the game right there with those homers in the first inning," said De La Rosa, who allowed one run and six hits in seven innings.
Gonzalez has five homers in his last three games and Arenado has connected in a career-high five straight games.
"We're starting to hit the ball a lot better," said Arenado, who got a hug from Gonzalez after his homer. "We were pumped up and it was a lot of fun. It was cool to do that."
De La Rosa (9-6) didn't walk a batter and struck out seven. Two of the strikeouts came in the sixth inning, helping him get out of a jam and he induced an inning-ending double play grounder from Juan Perez after giving up a one-out single to Kelby Tomlinson in the seventh.
John Axford worked a scoreless ninth for his 19th save.
Chris Heston (11-9) went 5 2-3 innings for the Giants and allowed seven hits and two runs, both on the solo homers in the first.
The Giants are in the midst of their third losing streak of at least seven games, including an 0-5 start to their current 10-game road trip.
"It's a tough stretch, no doubt about it," the Giants' Buster Posey said. "Be lying if you said it wasn't. We've got to find a way to turn it around though. It's all you really can do. You can't feel sorry for yourself, you can't pout. You just have to come ready to play and hope tomorrow is the day that we get back on track."
Gonzalez hit a towering drive in the first inning that narrowly sailed foul. He hammered the next offering from Heston over the wall in center field for his 36th home run of the season, extending a career high. Arenado followed by connecting for his 35th of the season, joining Dante Bichette (1995) and Larry Walker (1999) as the only Rockies to homer in five straight games.
It was the second time this season that Gonzalez and Arenado teamed to go deep in successive at-bats.
"It's been a frustrating year," Rockies manager Walt Weiss said. "(But) I think the guys are in a good place right now, playing good baseball right now. It's a close group of guys and we want to finish strong."
San Francisco pulled to 2-1 in the sixth on a one-out RBI single by Angel Pagan. Matt Duffy singled and Posey was hit by a pitch around a strikeout by Brandon Belt to load the bases. But De La Rosa escaped further damage by striking out Marlon Byrd.
Rockies first baseman Justin Morneau, reinstated from the disabled list before the game, played for the first time in nearly four months after being sidelined by concussion symptoms. He singled in his first at-bat and finished 1 for 4.
Giants: SS Brandon Crawford played for the first time in four games. He missed the previous three games because of a calf injury suffered Monday when he was hit by a pitch in a game against the Los Angeles Dodgers. ... INF Joe Panikhas begun a rehab assignment with Triple-A Sacramento. He has missed the last 32 games with a back injury.
Rockies: Utility player Matt McBride was designated for assignment to clear a spot on the 40-man roster for Morneau.
Giants: RHP Jake Peavy (4-6) faces Colorado for the first time this season. He's 5-7 with a 3.95 ERA in 20 previous starts against the Rockies.
Rockies: RHP Chad Bettis (6-4) is 1-0 with a 4.09 ERA in two starts since returning from a six-week stint on the DL due to inflammation in his pitching elbow.