The court scheduled the appeal for Sept. 30 in Florence, ANSA reported.
Knox and Raffaele Sollecito, her Italian boyfriend at the time, were convicted in 2009 of killing Meredith Kercher but an appeals court in Perugia, where the killing occurred, acquitted them. Italy's top court in March returned the case to the appeals court.
Italy's top court said the appeals court dismissal of forensic evidence was flawed and it found the prosecutor's theory -- a sex game gone wrong -- could offer the best explanation of what happened.
Rudy Guede was convicted of murder in Kercher's death but the court said he unlikely acted alone.
Kercher's family welcomed news of the retrial while Knox, who returned to the United States, and Sollecito reaffirmed their innocence.
Knox, who has written a book about her experience, is in Seattle and unlikely to attend the Florence trial. Sollecito has said he has nothing to worry about from the new trial.