The victory came on Kenseth's 41st birthday, and it was his first win with JGR.
"I just knew it," Kenseth said in victory lane. "I felt real good about this group. This is just the beginning."
Kahne finished second after leading 113 of 267 laps. Reigning Sprint Cup champion Brad Keselowski finished third and Kenseth's JGR teammate Kyle Busch was fourth in the No. 18 Toyota.
"I had an unbelievable Farmer's Insurance Chevrolet all day," Kahne said. "I drove so hard every single lap."
Keselowski started the race from the pole after rain canceled qualifying on Friday, forcing NASCAR to set the starting grid by 2012 owner points. Keselowski held the lead for the first 10 laps before losing the top spot to Kahne, who started the race from the third spot.
By lap 25, Busch made his way to third after starting the race 13th. But a pit road speeding penalty during a cycle of green-flag pit stops on lap 45 put Busch at the back of the lead lap. After the cycle completed, Kahne was back in front, with Keselowski in second.
Jimmie Johnson took second from Keselowski on a restart following the first caution of the race, which came out for debris on lap 66. A few laps later, he got by his Hendrick teammate, Kahne, for the lead.
Kahne retook the lead from Johnson on lap 138 and pulled out to a cushion of more than three seconds in fewer than 12 laps. He lost that cushion, and also the lead, when Marcos Ambrose brought out the second caution of the race on lap 160.
Johnson got off pit road ahead of Kahne to retake the lead. By that time, Busch was back toward the front and was able to get off pit road in the third spot.
Busch drove from third to the lead when the race went back to green, but with 84 laps to go, Kahne passed him to take the lead.
The yellow flag waved again for Bobby Labonte on lap 195. Denny Hamlin stayed out for track position to restart with the lead after falling back from a pit road speeding penalty earlier in the race.
Hamlin didn't stay up front for long, though, as both Kahne and Busch passed him on the restart to claim the top two spots. Busch took the lead after he and Kahne got by Hamlin, but Kahne retook the top spot with 57 laps to go.
Hamlin was forced to make a green-flag pit stop with about 47 laps to go after staying out during the previous caution. A yellow flag caught him a lap down a few laps later when the caution flag waved for Travis Kvapil with 44 laps remaining. That was before everyone else had made their final pit stops.
With the yellow out, everyone else was able to make their final pit stops under caution. Kenseth got off pit road first, Keselowski second and Johnson third, while Kahne lost time on pit road trying to miss the No. 14 of Tony Stewart. Kahne got off pit road sixth.
Kenseth and Keselowski maintained their positions in first and second until the fifth and final caution of the race came out for Ryan Newman with 32 laps to go. The leaders stayed out, and once again, Kenseth and Keselowski restarted first and second.
Kahne got by Keselowski to take the second spot on the restart and pulled away from the rest of the pack.
In the closing laps, Kenseth and Kahne waged a two-car battle for the win, while Keselowski and Busch raced for third. Kenseth was able to keep his car in front of Kahne the rest of the way.
"I was real nervous all day," Kenseth said. "He (Kahne) had the best car. . . . We were in the right place at the right time."
Keselowski and Busch swapped third back and forth before Keselowski finally settled into third place.