But Melissa King says she's not stepping down because of the sex video that has surfaced. King, who is 18, told The (Wilmington) News Journal she was aware of the video, but denies appearing in it.
Pageant officials say King is being represented by Hagerstown attorney J. Gregory Hannigan. The attorney told the newspaper that a statement on the resignation will be issued.
Pageant spokeswoman Dara Busch says the pageant's runner-up will replace King. The pageant's website lists Hailey Lawler of the Newark area as the 2012 runner-up.
Melissa King won the title of Miss Delaware Teen USA in November of 2012.
King, a Philadelphia college student from Bethany Beach, officially resigned as Miss Delaware Tuesday.
The Associated Press contributed to this report.