The Olympian reports that 19-year-old Alex Salazar entered his plea Thursday.
Court papers say the rape occurred in May 2013 after Salazar and the girl left the Great Wolf Lodge hotel in Grand Mound and went to an unknown location in Salazar's car.
The Oregon girl and her family were on vacation at the resort.
Court records say Great Wolf Lodge fired Salazar from his lifeguard job after the allegations surfaced. He had no prior criminal record.
Sentencing is expected in March in Thurston County Superior Court.
Grand Mound is south of Olympia.