"Mr. Jackson was not aware and he is extremely upset that his memorabilia was included amongst the memorabilia that is being auctioned off," said spokeswoman Raymone K. Bain.
The Jacksons Auction is scheduled May 30-31 at the Hard Rock hotel resort.
Guernsey's auction house said items include Michael Jackson's gold record for his "Thriller" album, handwritten lyrics for The Jackson Five hit "ABC" and a "Victory Tour" program signed by Jackson family members.
Arlan Ettinger, founder and president of Guernsey's, compared the sale to an auction of Elvis Presley/Graceland memorabilia he conducted in Las Vegas in 1999.
"It certainly is in that sphere of landmark, high-profile, extraordinary auctions," Ettinger told The Associated Press on Wednesday.
Michael Jackson, 48, has been living in Las Vegas while he evaluates proposals for a comeback after his 2005 acquittal in California on child molestation charges.
His father, former Jackson Five manager Joe Jackson, also lives in Las Vegas. He didn't respond to a phone message seeking comment.
Ettinger said the collection was owned by luggage transportation company Universal Express Inc., of Boca Raton, Fla., which bought it last year from a New Jersey construction company owner.
The former owner, Henry Vaccaro, claimed a warehouse full of Jackson memorabilia after a failed business venture wound up in bankruptcy court. Michael Jackson and his sister Janet Jackson sued to stop Vaccaro from taking ownership, but a Los Angeles judge threw out Michael Jackson's claim in 2006.
The status of Janet Jackson's claim was unclear Wednesday. Messages left with her publicist weren't immediately returned.
Other items include a test pressing of The Jackson Five's "I Want You Back," Marlon Jackson's glitter jacket, Randy Jackson's futuristic 1984 stage boots and a white fedora believed to be from Michael Jackson's "Bad" album music video.
By Ken Ritter