Cruising from the outside, Kahne got the jump he needed, zipped past Gordon and pulled away with two laps left Sunday to win at Pocono Raceway.
"I about gave it away when Jeff got by me," Kahne said.
Kahne recovered in the No. 5 Chevrolet for his second victory of the season, all but securing his spot in the Chase for the Sprint Cup championship. He had the car to beat for the final half of the 400-mile race until a late caution bunched up the field.
Gordon nudged past Kahne after some thrilling two-wide racing and seemed poised to win at Pocono for the seventh time. After the final caution, Kahne was simply too fast, too strong to be denied his first win at Pocono since 2008.
So close to the checkered, this loss stung Gordon. Even worse, his runner-up finish came on his 42nd birthday in his 42nd career Pocono start.
"I thought all I needed to do was get … to the bottom and I'd be good," Gordon said. "He got a killer run and blasted by on the outside of me. Caught me by surprise. It just kills your momentum."
Kurt Busch, who also celebrated a birthday, Ryan Newman and Dale Earnhardt Jr. rounded out the top five. The top five cars were Chevrolets.
Busch helped out Kahne with one final push down the front stretch to find some needed speed.
"That was kind of the race at that point," Kahne said. "Once I cleared [Gordon] getting into two, from there it was just, don't make a mistake and try to run the quick lap on the last one."
Kahne, Gordon and Earnhardt made it an outstanding race for Hendrick. Teammate and series points leader Jimmie Johnson was 13th after a blown tire knocked him out of the lead.
Kahne had stretched his lead to almost 8 seconds when a caution for debris came out with 12 laps left. Gordon, who won at Pocono each of the last two years, was strong in the No. 24 and had the lead as he tried to extend his record for career wins at Pocono.
Matt Kenseth spun with four laps left to erase Gordon's lead and set up the thrilling finish. Gordon led again until Kahne ran him down with a hard, sweeping run past his teammate for the win.