The 63-year-old comedian and Oscar-hosting veteran said on Twitter that he is "doing the Oscars so the young woman in the pharmacy will stop asking my name when I pick up my prescriptions."
Academy officials have confirmed the appointment, following the departure of Eddie Murphy. Crystal last hosted the show in 2004. This will be his ninth stint as host.
The move to name Crystal as Oscars host comes after a groundswell of sentiment for his return following a guest appearance on the 2011 show for which he received a standing ovation.
He said later he was moved by the warm reception and that "it might be fun" to host the show again.
"I think the show needs to change," he said in an interview in March. "There's too many awards and it has to sort of freshen itself up, and if I can be a part of that, that would be great."
Crystal previously hosted in 1990-93, 1997/98, 2000 and 2004, some of the most successful shows in Oscar history.
The past two ceremonies featured the duos of Anne Hathaway and James Franco and Steve Martin and Alec Baldwin, while Hugh Jackman hosted solo in 2009.