Posting an adorable snap on Instagram, Chris wrote: "Met the real superheroes of the world at @ladycilentochildrenshospital. A huge shout out to all the brave kids who are an inspiration to all of us!"
The hospital itself added: "Thank you @chrishemsworth and @twhiddleston for creating some superpowered memories for our patients!"
They're the latest Marvel stars to do their bit for sick fans, after Robert Downey Jr, Chris Evans and Gwyneth Paltrow visited an ill teenager earlier this year.
Thor: Ragnarok plot, cast, release date, spoilers and everything you need to know
Ryan Reynolds also recently paid a moving tribute to 13-year-old Deadpool fan Connor McGrath, who died following a battle with cancer earlier this year.
Chris Pratt and Chris Evans agreed to dress up in character for a visit to Boston's Christopher's Haven children hospital in 2015 too.
Chris Hemsworth and Tom Hiddleston will star alongside each other in Thor: Ragnarok, which is released on October 27, 2017, in the UK and November 3, 2017, in the US.