The pageant is to take place April 11.
NBC said this is the first time the brother-sister duo will have presented a prime-time special together since 2000. It also marks the third time they will have been the pageant's hosts.
The pair is best known for its 1970s prime-time variety show "The Donny & Marie Show" and daytime talk show "Donny & Marie," which ran from 1998 to 2000.
Donny and Marie Osmond also plan to reunite on stage for eight sold-out shows at the MGM Grand in Las Vegas in July, NBC said.
"Watching the pageant was an anticipated yearly event when Donny and I were growing up," Marie Osmond said in a statement. "We are honored to be a part of this U.S. tradition and to hopefully make Miss USA a memorable night for millions of new viewers."
"We are so excited to have such television icons as Donny and Marie host our show," said Phil Gurin, executive producer of Miss USA Pageant 2008.
Couple mistakenly served bag of cash at McDonald's drive-thru
Kate Middleton recycles dress at movie premiere