Melissa King, 18, resigned the day after a porn website posted a video that claimed to feature the 2013 beauty queen
"I would like to confirm to you that the Miss Delaware Teen USA pageant has received a resignation letter from Miss King's attorney," Dara Busch, pageant spokeswoman, wrote in an e-mail to the News Journal in Delaware.
The woman in the porn looks like King and admits to a man off-camera that she has competed in beauty pageants.
But when contacted by the newspaper, King denied it was her in the clip.
On Tuesday night, @Melissa_M_King retweeted on Twitter, "If a good person does a bad thing, it does not make them bad."
The runner-up, Hailey Lawler, will take King's place, officials said.
Miss Delaware Teen USA is operated by the Miss Universe Organization.