Hamlin pitted with 21 laps to go and took right side tires and fuel to get back on the track.
Harvick, who beat Hamlin to the checkered flag in Saturday’s race at Pocono, closed the margin between the pair, but there wasn’t enough time left for him to catch Hamlin. Harvick finished runner-up, tailing away in the last couple of laps to end up more than three seconds behind Hamlin at the checkered flag.
In winning his 41st career Cup race, Hamlin tied Jeff Gordon for most career Cup wins at Pocono. Hamlin’s six wins have come in 14 years at the 2.5-mile Tricky Triangle.
“Six? I can’t put it into words how much it means to me,” Hamlin told FS1 after the race. “I was hoping for no caution. I knew the car I had. I didn’t want to make any mistakes like at Bristol, where I gave that one away.”
Hamlin’s five previous wins at Pocono came in 2006 (twice), 2009, 2010 and last summer.
“I don’t think this will be the last one,” Hamlin said during a post-race media teleconference. “I think we’ll continue to build on it. I really wanted to win both races but it didn’t work out. I don’t want to be greedy.”
With the second-place finish, Harvick earned his 11th top-10 finish of the season and his 19th top-10 career finish in 40 starts at the Tricky Triangle, including five runner-up showings.
Ranking No. 1 in driver points, Harvick leaves Pocono with a commanding 52-point lead over Ryan Blaney in the Cup point standings.
“Our car today was actually better than yesterday,” Harvick told FS1. “(Hamlin) just did the opposite than we did. We didn’t want to get caught a caution and wound up losing too much time in lapped traffic. He was out there running clean laps and waited to the very end and wound up in front of us. (Saturday), that won us the race and today we finished second.”
The cars of Harvick and Martin Truex Jr. were each found to have one unsecured lug nut. There were no other post-race inspection issues.
The start of the race was delayed more than 30 minutes due to lightning. Then, after the first six laps under green flag conditions, there was a nearly one-hour delay due to rain.
STAGE 1 WINNER: Kurt Busch
STAGE 2 WINNER: Brad Keselowski
Who had a good race: Erik Jones earned a season-best third-place finish, as well his sixth top-10 finish in eight career starts at Pocono. … Aric Almirola earned his fourth consecutive top-five.
Who had a bad race: Kyle Busch was battling with Ryan Blaney on Lap 76 when he spun and wrecked, leaving Busch winless this season. … Michael McDowell, who had a strong eighth-place finish in Saturday’s race, spun and hit the wall hard on Lap 16. He finished last in the 40-car field.
Notable: Sunday marked the first tripleheader in NASCAR history, where all three national series raced at the same location and on the same day. … Cole Custer (17th) was the highest-finishing rookie.
What’s next: Brickyard 400 at Indianapolis Motor Speedway; at 4 p.m. ET July 5 on NBC.