The actor revealed his dad is in the grips of the devastating condition, which causes severe memory loss and confusion.
He tells America's Parade magazine, "My dad is fairly well into Alzheimer’s now. His short-term memory is pretty much gone. He still recognises me and can talk about the past, and weirdly, he’s as happy as I’ve ever known him, which is wonderful.
"One of the joys of doing The Wolverine was being in Sydney and spending time with him."