The Kamehameha Schools sent letters to parents alerting them of a mumps case at the Kapalama campus.
It was not made clear whether the affected person was a student or a staff member.
The school said it is working with the Department of Health on the case and warned parents to monitor their children for symptoms.
Those symptoms include: swollen glands, fever and headaches.
There was a mumps outbreak in 2017, the DOH declared it was over in October 2018.
More than 1,000 people were sickened during that outbreak.