The UNICEF ambassador is auctioning off the Catherine Dean frock that she wore in her A Year Without Rain video to raise money for UNICEF, who aim to help disadvantaged children.
The Disney star told People.com: 'It's a beautiful dress.
'It was obviously a very important part of the video - we wanted it to be very beautiful and very flowy and I got lots of great comments on it so I thought it would be awesome to give it to charity.'
The gown is available from now until November 10 via the auction site Charitybuzz.
Gomez, 18, is also auctioning off the chance for a person and five friends to watch her perform and meet her during her first-ever acoustic concert at The Roxy Theatre in West Hollywood, Los Angeles on October 26.