"Our thoughts and support are with Steve and his family," Nickelodeon tweeted Tuesday.
"I wanted people to hear directly from me that I have been diagnosed with ALS," Hillenburg said in a statement.
"Anyone who knows me knows that I will continue to work on 'SpongeBob SquarePants' and my other passions for as long as I am able. My family and I are grateful for the outpouring of love and support. We ask that our sincere request for privacy be honored during this time."
Variety cited an unnamed source close to Hillenburg as saying the 55-year-old writer and animator is in the early stages of the disease.
Copyright 2017 United Press International, Inc. (UPI). Any reproduction, republication, redistribution and/or modification of any UPI content is expressly prohibited without UPI's prior written consent.