Copperfield's lawyers Angelo Calfo and Patty Eakes deny the allegations and say the lawsuit is "extortion for money, plain and simple."
No criminal charges have been filed.
The Seattle Times describes the woman as a 22-year-old fashion model and former Miss Washington USA contestant. She says she met Copperfield during a January 2007 performance in Kennewick and that year she was invited to his private island.
The Times says the lawsuit was filed July 29 in federal court in Seattle against David Seth Kotkin, Copperfield's given name. That date was the deadline for a two-year statute of limitations.