Moments after van Gisbergen took the lead with 16 laps to go, a yellow flag caution stopped the race for an ambulance needed to assist someone in the infield.
The race resumed with 13 laps to go only for another caution, the sixth of the day. It eventually resumed with nine laps remaining and van Gisbergen held off a fast-chasing Tyler Reddick on fresh tyres.
With Reddick closing in, another caution with one lap to go ensured van Gisbergen would take the chequered flag. Ty Gibbs finished second with Reddick taking third.
The victory capped off a brilliant day for New Zealand drivers in the US after Scott Dixon claimed his 59th IndyCar win.
“I love this place. What an amazing weekend for me. Lucky guy to drive some great cars...hope we put on a good show,” van Gisbergen said after completing his tradition of kicking a signed rugby ball into the stands.
“We made no mistakes. There was some really fast cars and we just seemed to get it right. It was just so hot the weekend, the track was so slick, the times were a lot slower and the margin for error was very tiny. We just had to get it right. I’m rapt,” he added.
The second win of the season moves Van Gisbergen to fifth spot in the playoff standings
Van Gisbergen will head into the next race at Sonoma Raceway as the favourite, another road circuit before a stretch of three oval races.