The Australian hunk was filming the latest installment of the X-Men franchise in Asia when he was given two days off - but instead of sit back and relax, he decided to scale Mount Fuji with 12-year-old Oscar.
And Jackman admits it was an adventure to remember.
He tells U.S. TV host Jimmy Kimmel, ""We actually did shoot in Japan. And that was incredible... It was an experience I will never forget. Luckily we had two days off, so I climbed Mount Fuji with my son Oscar. He's only 12. It's a serious climb...
""It takes two days. So you stay overnight. They drive up, there's 10 stations... and each station is a couple hours climb, and we ended up staying on the eighth station... We get there at about 5.30pm and you then sleep until about 1.30 in the morning and climb the rest.
""Now in Japan, in these log cabins, they give you a little meal and you all go to sleep in these little shelves... They all, just like sardines, pile in, and you see all the Japanese people (acting) like this is absolutely normal... And they give you a packet of rice as a pillow... 1.30 in the morning we all get up... and we get to the top of the mountain and we arrive 10 minutes before sunrise. It's getting brighter, the sun is coming up, and it was amazing!""
But Jackman admits the gruelling trek was too much for his kid, adding, ""Just as the sun came up, I look down at my son Oscar and he literally (is fast sleep). He has no recollection of the entire thing.""