US auction house Guernsey's has put 1,100 items on display which were once owned by music's Jackson family.
Everything is being sold in Las Vegas this Wednesday and Thursday, with millions of dollars expected to be raised.
A prototype sculpture of film character ET, which belonged to Michael Jackson, will be one of the lots to be auctioned.
Michael - whose bullet-proof vest is being sold - had gone to court to try to stop the auction from taking place.
However, he dropped his case after accepting that he had no legal right to the items, now owned by film studio Universal.
Some of sister Janet's belongings are also available, including a frilly pink dress she wore aged eight at the MGM Grand.
Paintings of iconic Jacksons images - including a Walk of Fame star and the cover to Michael's Off the Wall - are up for sale.
The auction house believes it is a "once in a lifetime" sale, saying the collection is highly unlikely to be rivalled.
Michael Jackson has been invited to attend the auction, but it is unclear whether he will head to Las Vegas.
All of the merchandise is on display at the Hard Rock Hotel and Casino until bidding begins on Wednesday.