The 20-year-old has cleared out her closet to benefit the Free The Children organisation, which helps youngsters in developing countries.
Lovato's dresses and tops are available on a website, and she is keen to raise as much funds as possible, reports a web portal.
In a post on her auction homepage, she writes: "I hope you will enjoy wearing these awesome clothes as much as I have! Thank you so much for helping me support Free The Children. I really believe in all of the great work they are doing for young people everywhere."