The 'Hero' singer has put a hot pink, fishtailed asymmetric frock onto the auction website to raise money for breast cancer charity Susan G. Komen for the Cure.
The gown was created by Julian Contreras as part of a competition where the singer asked fans to design a dress inspired by her Deicious Pink fragrance. It is one of only three in existence.
Mariah was last seen wearing the dress on a dinner date with husband Nick Cannon in Calfiornia in April.
The close-fitting dress will be listed until May 30.