Guentzel and Letang each had a goal and an assist for the Penguins (22-10-5), who are 3-2-0 on their six-game road trip.
"Give San Jose credit, they played really hard, but we didn't play the type of game that we're capable of in the first 40 minutes," Pittsburgh coach Mike Sullivan said. "I thought the last 20 was a step in the right direction. We certainly played better, and obviously Sid and Jake made a great play in the overtime, but I think that was the difference."
Rudolfs Balcers scored, and Adin Hill made 25 saves for the Sharks (20-17-2).
"We did some good things, but the only thing we didn't do was score," San Jose coach Bob Boughner said. "A lot of our guys are snakebit. We had guys in front of the net but we're not putting them in. We had 41 shots, tried to make it hard on their goalie, just not a lot of puck luck."
Balcers gave the Sharks a 1-0 lead at 7:01 of the first period when he redirected a shot by Erik Karlsson from the right face-off circle.
"We had a lot of good chances," San Jose forward Logan Couture said. "I liked our game. If we continue to play this [type of] game, you're going to win more than you're going to lose."
Letang tied it 1-1 at 10:56 with a backhand on the rush.
"We have to stay positive," Sharks defenseman Mario Ferraro said. "We played a really good game tonight. There will always be struggles to put the puck in. We'll obviously study on ways to improve."