With Pittsburgh trailing 2-0, Letang cut the deficit in half midway through the third when he intercepted Sheldon Brookbank's pass near Chicago's blue line and backhanded a shot past Nikolai Khabibulin to make it 2-1 with 10:31 remaining.
Letang's second goal came via the power play. With Theo Peckham in the penalty box for high sticking, Letang ripped a slap shot past Khabibulin with 2:16 left.
"We got one real power play and we got a chance to capitalize on it," Letang said. "We had great looks, great chances. I think we did a good job moving the puck, shooting the puck. The power play looked good for the first time that we were all together on the ice.
"We didn't really play any games with our full lineup. It's tough to adjust and even if we've been together for a while, it's training camp and you try to get the rust off."
Bryan Bickell scored two goals for Chicago. His first came shorthanded 1:09 into the second period, when he slapped the puck out of midair and past Penguins goalie Jeff Zatkoff to give the Blackhawks a 1-0 lead. He made it 2-0 via the power play with six minutes left in the second, redirecting Jeremy Morin's slap shot past Zatkoff.
"(Bickell) is a big body and he can see pucks and he's got a great shot as well," Blackhawks coach Joel Quenneville said. "He's got that capability of scoring those types of goals and he'll probably be playing with a couple of guys who can get him the puck too. So, we expect his production to be better than it's been."