Trailing 3-0, Hillgrove used an interception to score its first touchdown on a 4-yard pass from Kelvin Cameron in the second quarter.
The Hawks recovered a Pebblebrook fumble on the first offensive series of the second half and turned it into a touchdown on a 3-yard run by Gage Henry. They then took advantage of yet another Falcon fumble on the ensuing kickoff and went on to score on an 11-yard run by Justin Cone to give them their eventual margin of victory.
The win put Hillgrove (5-2, 3-2) into a four-way tie for second in the region with North Cobb, South Cobb and Harrison.
Meanwhile, Pebblebrook (3-5, 2-3) fell into the lower tier of the standings with the loss, now sixth place, just ahead of Kennesaw Mountain and Campbell.
Though Hillgrove was able to capitalize on two of the three turnovers that its defense forced, Hillgrove coach Phil Ironside acknowledged that the Pebblebrook defense kept his team from taking advantage of further opportunities that the Hawks' defense provided.
"Our defense kept giving us the ball (Friday) and we didn't take advantage of it and score and kind of take the burden off of us," Ironside said. "A lot of that goes to Pebblebrook. Their defense is tough, probably the best defense we've faced this year. They did a good job and their kids played hard."
Henry rushed for 88 yards on 13 carries and ran for one touchdown, while completing 19 of 30 passes for 166 yards and throwing for another score to lead Hillgrove.
After a scoreless first quarter, Pebblebrook got on the scoreboard first on a 33-yard field goal by Dennis Gallo with 9:08 remaining in the first half to put the Falcons up 3-0.
However, things began to turn around for Hillgrove later in the second quarter as cornerback Justin McCloud intercepted a pass from Pebblebrook quarterback C.J. Goodman with 5:21 remaining in the first half.
Henry took control for Hillgrove on its next series as he ran with or threw the ball on all seven plays, including his 4-yard scoring pass to Cameron with 2:47 left in the half. Andrew Goughen added the extra point to put the Hawks in front 7-3, a lead which they held at halftime.
Pebblebrook drove into Hillgrove territory on the first drive of the second half, with a 21-yard run by Harris putting the Falcons on the Hawk 43 with 10:32 remaining in the third quarter.
However, Hillgrove recovered a Pebblebrook fumble on the next play and took over the ball at its own 45-yard line with 10:10 left.
Hillgrove proceeded to go on a 10-play, 55-yard drive that concluded with Henry's 3-yard touchdown run, giving the Hawks a 14-3 lead following Goughen's extra-point kick with 7:28 left in the third quarter.
Hillgrove got the ball back almost immediately as linebacker Dylan Mitchell recovered a Pebblebrook fumble on the ensuing kickoff and took the ball over again on the Falcon 25 with 5:58 left in the third quarter.
This time, it took only four plays for Hillgrove to take advantage of its opportunity as Cone put together runs of 2 and 7 yards before entering the end zone on his 11-yard run with 4:24 left in the third quarter. Goughen's extra-point increased the Hawks' advantage to 21-3, where it stayed the rest of the way.
Pebblebrook coach Randall Smith was disappointed about the turnovers, but was proud of his team's effort in what was a crucial game for his Falcons.
"Basically, that's a playoff game. That's what we're going to see (if we make the state playoffs)," Smith said. "You get an early turnover, you can fight through it, but when you get two in the second half and have a quick turnaround right after halftime, it does put you in the hole. The kids fought through it. They've got their chin up and we're just proud of their effort."
"They could have just laid down and let (Hillgrove) put 40 points up and they kept fighting. If we can learn not to shoot ourselves, hopefully we can pull out one of these big game out and take another step up the ladder."