The world endurance team said Vettel, a 53-time grand prix winner who left Formula One at the end of 2022, will drive the Porsche 963 hybrid prototype at the Motorland Aragon circuit as part of a 36-hour test.
The German has already spent time in the simulator as well as carrying out some test laps at Porsche's Weissach test track on Thursday.
"I've always followed other racing series and my curiosity for endurance events encouraged me to just give it a shot," said Vettel, who won his F1 titles with Red Bull and whose last race was with Aston Martin.
"Now I’m excited about the long run in Aragon and I’m looking forward to my time behind the wheel. It’ll definitely take an adjustment and some getting used to but everyone in the team is very open and helps me.
"This will be a new experience for me. We will then see what happens next in this respect - at the moment there are no further plans for the future."
Vettel, who is outspoken on the environment and has campaigned for renewable energy, said in 2022 that climate change had made him question his F1 job.
Le Mans cars run on 100% renewable biofuel derived partly from wine industry residues.
The Le Mans 24 Hours race is on June 15th-16th with Porsche aiming for a 20th outright victory at the Circuit de la Sarthe and the factory team entering three 963 cars with the third lineup as yet undecided.
