Busch held off Tony Stewart for second in his 200th career start. Points leader Kevin Harvick was fourth, followed by four-time defending series champion Jimmie Johnson.
The start was delayed 90 minutes by rain then another 10 minutes or so while officials patched a pothole at the end of pit road inadvertently opened up by a jet dryer. Once the rain cleared, Hamlin dominated at one of his favorite tracks.
Hamlin appeared to have the race won five minutes earlier, but his 2-second lead was wiped out when Harvick nudged Joey Logano into the wall while the drivers were battling for fourth with less than two laps to go. Hamlin couldn't quite reach the start/finish line for the white flag before the caution came out, sending the race into a two-lap overtime.
Hamlin debated on which lane to pick for the restart, and opted to go inside in front of Busch. The two Joe Gibbs Racing teammates haven't exactly been friendly of late, with Busch saying he wanted to "kill" Hamlin following a run-in at the All-Star Race two weeks ago.
There was no drama this time. Hamlin easily drew free of Busch and Stewart, cutting Stewart off as they exited the first turn and cruising from there.
"That last restart was the best [the car] has been all day," Hamlin said.
The finish line was almost in sight when a massive wreck swallowed nine cars. Jeff Gordon, Mark Martin and Kasey Kahne were all involved, with Kahne's No. 9 Dodge on top of the retaining wall as one of the circuit's more sleepy stops ended in chaos. None of the drivers were hurt, but tempers across the garage were frayed.
The 20-year-old Logano exchanged words with Harvick and had to be restrained by Harvick's crew, a rare display of anger from the normally reserved Logano.
Stewart, while admitting he didn't have enough car to chase down Hamlin, wasn't pleased either. He called the racing off the restarts "idiotic" and left little doubt that he'll seek payback starting next week in Michigan.
"I've seen some of the worst driving I've ever seen in my life in a professional series right here [Sunday]," he said. "So for anybody that's looking for drama for the next couple races, start looking because I can promise I'm going to start making the highlight reel the next couple weeks."
Hamlin's been a highlight reel fixture all season, and had little trouble enjoying his fourth win in his past nine starts.
He celebrated with a lengthy burnout and ended up nicking the wall in the process. He might want to take care of the car, which is 3-for-3 on the season.
Pocono 500 Results