Johnson, who led 289 laps, picked up his second victory of the season, in addition to a win in the Sprint All-Star Race on May 19, and his second victory in the past three points races. Hendrick drivers now have won four consecutive races, including the All-Star event.
The victory was the 57th of Johnson's career, eighth most all-time. His seventh win at Dover tied Richard Petty and Bobby Allison for most at the high-banked, 1-mile concrete track.
Harvick came home second, 2.550 seconds behind Johnson. Kenseth ran third, followed by Dale Earnhardt Jr. and Clint Bowyer. Greg Biffle retained his series lead by one point over Kenseth with an 11th-place finish.
Those who have decried the recent lack of caution flags in Cup races got more than their fill on Lap 9, when contact Tony Stewart and Landon Cassill triggered a 12-car pileup off Turn 2.
Regan Smith ducked to the inside and tried to power past Stewart but couldn't clear the No. 14. Nine other cars stacked up behind Cassill, Stewart and Smith, blocking the track and necessitating a stoppage of 19 minutes, 54 seconds while track workers cleaned up the mess.
Smith blamed himself for the wreck, but Stewart was magnanimous in relieving Smith of responsibility.
"I got into the back of the No. 14 and started the whole thing," Smith said. "I'll take full blame for that. Somehow they got checked up in front of me. I just didn't have time to get slowed up with it. I hate that there are so many wrecked race cars here. It's not fun for anybody."
Stewart's take on the accident was quite different.
"The No. 83 [Cassill] was trying to get back down to the bottom and we were just in the wrong place at the wrong time," Stewart said. "It wasn't Regan's fault. He was right behind us and he didn't have anywhere to go either. Just not a real good deal at the beginning of the race like this."