The Frenchman was one of several drivers to gamble on fuel strategy, and made it stick for the final 29 laps Saturday to earn his third career IndyCar victory. He took the lead when Oriol Servia had to stop with four laps remaining, and Pagenaud managed to make it to the finish despite having to keep one eye on his mirrors.
Ryan Hunter-Reay was second and Helio Castroneves third on his 39th birthday.
"Man I didn't know what we were asking for, but we made fuel," Pagenaud said in Victory Lane. "The fuel saving was amazing. It was nerve-wracking. I was worried about RHR coming back, and I didn't know what Helio was doing here. I don't like racing off throttle."
Sebastien Bourdais and Charlie Kimball rounded out the top five.
James Hinchcliffe was taken from the track on a stretcher and transported to a hospital, where he was diagnosed with a concussion after he was hit in the head with debris. A replay appeared to show debris from a car in front of him flew into his cockpit following a restart.
IndyCar said he'll have to be re-evaluated before he's cleared again to drive. Preparations begin Sunday for the Indianapolis 500, with qualifying scheduled to begin next Saturday for the May 25 race.
IndyCar policy in the past has been to hold a driver with a concussion out of the car a minimum of seven days.
"I was actually next to him on track and all of a sudden debris went everywhere and he slowed up," Hunter-Reay said about his Andretti Autosport teammate. "It was something that happened in front of him and he was hit."
The race began with a violent wreck when pole-sitter Sebastian Saavedra stalled on the standing start. He was hit by multiple cars, and debris struck Indianapolis Mayor Greg Ballard as he waved the green flag.
Saavedra's car simply didn't go when the lights went out and, after Hunter-Reay frantically darted around him, Saavedra was clipped by Carlos Munoz and then hit hard from behind by Mikhail Aleshin.
"We just followed protocol at the start," Saavedra said. "As soon as I released the clutch, it went from 11,000 rpm to zero. This should not have happened, unfortunately."
The initial hit from Munoz didn't seem too bad, but Aleshin's direct hit sprayed debris all over the track, sending spectators and track workers standing along the wall scrambling for cover. Saavedra was seen in his cockpit with his arms in the air anticipating a potential collision as cars tried to weave their way around his stalled KV Racing car. He was visibly upset after the accident as he talked to his team on his pit stand. He had won the first pole of his career — in part because Hunter-Reay had his two fastest laps disallowed for causing a caution in Friday's qualifying — and was looking for a strong finish at the famed race track.
"Man, we had an opportunity to be at the front of the pack in this amazing place. We wanted to bring it home in the same place," he said. "To not even get a chance because of a freaking electrical thing ..."
It had many drivers complaining about the standing starts, which have been problematic since IndyCar began using them at some tracks last season. The incident damaged several cars one day before teams begin practice for the May 25 Indianapolis 500.
"I think IndyCar has had like two good standing starts since we started them last year," said driver/owner Ed Carpenter, who saw Mike Conway have to take his car to the garage for repairs after the accident. "Haven't been a fan, still not a fan."
Drivers also grumbled about the way race control was restarting the races, with the leader having to use a late restart zone. Graham Rahal said he was victimized when he was run into from behind by Juan Pablo Montoya.
"These restarts are pretty stupid. You can't see back there because the rear wings are so big, and the officials, we need to work with them to try to change this because there's going to be a lot of accidents," Rahal said. "I said the restart before, I said to my dad, 'Somebody's going to get hurt out here because you can't see.'
"They need to let the leader go earlier. Right now, the way it is, they're trying to be like NASACAR and this isn't NASCAR. We can't just bump-draft each other."