Edwards rallied after falling two laps down because of a flat tire, then beat Brad Keselowski off pit road for the lead 12 laps from the end and held on for his first Southern 500 victory Sunday night.
Edwards won the Coca Cola 600 in May and had six top-10s in the past seven races. Still, he was looking for a boost that would propel his first-year Joe Gibbs Racing program into the playoffs.
"This is what we needed," Edwards said. "We really needed a shot in the arm."
And now Edwards heads into the Chase bursting with confidence -- in the entire team. He was two laps behind after this flat around Lap 90. He was in 36th place on Lap 140. But there he was at the end, pushing pole-sitter Keselowski and defending Southern 500 winner Kevin Harvick 40 laps from the end.
Crew chief Darian Grubb made strong calls throughout the night, Edwards said, and his pit crew did the job at the most crucial time.
"Everyone did their job in this one," Edwards said after his 25th Sprint Cup victory.
Keselowski was second, and Denny Hamlin finished third. Joey Logano was fourth, followed by Harvick and the Busch brothers, Kurt and Kyle.
Edwards gave Joe Gibbs Racing its seventh victory in the last 10 events. JGR swept the weekend, with Hamlin winning the Xfinity race Saturday.
Edwards did his signature victory backflip in the race's return to Labor Day weekend.
"I guess we made it Carlington for a couple of minutes," Edwards said after his crew taped over part of the "D" on the painted Darlington sign along a retaining wall. "This is the Southern 500. This is amazing."
Edwards has won multiple races in season for the seventh time in 11 seasons as a fulltime driver.
Keselowski started on the pole and by far led the most laps with 196. But he was beaten out of the pits by Edwards on Darlington's record-setting 18th caution period with 12 laps left.
Almost as much as drivers enjoyed Darlington's throwback paint schemes and retro-1970s theme, they loved the low downforce package given the cars -- the same that was used to rave driver reviews in Kentucky earlier this year.
"Man, I loved it. This is as good as it gets," Edwards said about the low-downforce package. "This is what it's about: sliding cars, the tires falling off. If there's any way we can run this in the Chase, I hope we do it."
"It separates the race car drivers from the pretenders and that's the way it should be," he said.
Keselowski hoped to use Darlington to springboard into the Sprint Cup playoffs, which start in Chicago in two weeks. He said his team still has work ahead.
"Just one spot short at the end," he said. "We're right there. We've just got to find one more level to win these races and win this championship."
NASCAR's regular season ends next week at Richmond, where the field of 16 contenders will be set. Kyle Busch, with four victories, clinched a spot by guaranteeing he would finish among the top 30 drivers. Busch missed the first 11 races after a horrific crash in the Xfinity race at Daytona.
NASCAR returned the Southern 500 to Labor Day weekend for the first time since 2003. The track, the sport's oldest superspeedway, closed NASCAR's summer as one of its crown jewel events for 53 years until losing out in Sprint Cup realignment.
But NASCAR leaders thought the time was right to put the iconic race back in its traditional sport. The race featured a 1970s, throwback theme, with 35 teams racing in retro paint schemes.
Kyle Larson, his No. 42 sporting Kyle Petty's old Mello Yello colors, came out for driver introductions in a curly wig with a mustache grown for the weekend. NBC Sports got into the spirit, too, having Hall of Famers Ken Squire, Ned Jarrett and Dale Jarrett in the TV booth to call some of the race.
While the hype was huge, the true throwback was Darlington, which was the same tire-chewing track that's befuddled NASCAR's best for generations. Chase Elliott, running his last Sprint Cup race before slipping into retiring Jeff Gordon's seat in the No. 24 car next season, spun out just eight laps in to bring out a caution.
It was far from the last -- for Darlington and for Elliott. Bill Elliott's son, who won the Xfinity race here in 2014, was involved in another spin that took him out of the race for good.
Tony Stewart stayed out during one of the cautions while the field pitted and wound up leading for 10 laps, the first time he's run up front since Talladega last May. But Stewart was quickly run down by the pack of front runners, led by Harvick and Keselowski.
Edwards wins caution-filled race
Carl Edwards picks up his second win of the season with the victory at Darlington.