He cleared a meeting record of 6.15 metres at Place de la Navigation, two weeks after he captured his second consecutive Olympic title with a stunning world-record 6.25m jump in Paris.
The Swede needed just four jumps to clinch Wednesday's victory with a height of 6.0, then had the bar raised to a meeting-record 6.15, clearing it on his third attempt.
"It's always nerve-wracking when you have a big performance like I did at the Olympics," Duplantis told reporters. "I stepped out on the track today and I really loved it."
Olympic silver medallist Sam Kendricks of the US cleared 5.92 for second place. Norway's Sondre Guttormsen, Australia's Kurtis Marschall and EJ Obiena of the Philippines finished in a three-way tie for third with 5.82.
Duplantis wowed the Stade de France crowd at the Paris Olympics when he broke the world record for a ninth time.
The remainder of the Lausanne Diamond League programme is on Thursday at Stade Olympique de la Pontaise.
