The singer revealed the news about his oldest son Noah in a Facebook post on Friday.
“We are devastated about the recent cancer diagnosis of our oldest son Noah who is currently undergoing treatment in the US,” Buble said in a statement. “We have always been very vocal about the importance of family and the love we have for our children.”
“Luisana and I have put our careers on hold in order to devote all our time and attention to helping Noah get well,” he continued.
“At this difficult time, we ask only for your prayers and respect for our privacy. We have a long journey in front of us and hope that with the support of family, friends and fans around the world, we will win this battle, God willing.”
Buble and his wife Luisana Lopilato had Noah in August 2013. They welcomed another child this past January.