The 49-year-old actress has starred on the crime procedural drama since its premiere in 1999.
According to TVLine, the financial terms of Hargitay's new contract are yet to be determined, but it is likely that she will remain the highest-paid actress on TV.
For the 14th season of the show, Hargitay's contract demanded $500,000 (£330,000) an episode for a 24-episode run.
Hargitay tweeted the good news of her return on Saturday (May 25), when she wrote: "Happy weekend. It's official. Season 15--I'LL BE BACK!"
Law & Order: SVU is set to return for its 15th season this fall.