The pair has become close while shooting new movie The Place Beyond the Pines together - after a longtime friendship reportedly blossomed into romance.
And they weren't hiding their feelings for each other at the happiest place on earth on Saturday.
An onlooker tells Us Weekly magazine, "They were very playful. Eva was skipping around like a little girl... She would lean into him and she held his arm the entire time."
Photos published in the new issue of the magazine clearly show the couple is more than just friends and a source tells the publication, "It hasn't been a secret how excited Eva's been to film with him, and she's always joked with us about how gorgeous he is. She's never been shy about having the hots for him!"
Mendes recently split from longtime boyfriend, filmmaker George Augusto, and has been romantically linked to funnyman Jason Sudeikis, while Gosling has dated his The Notebook co-star Rachel McAdams and has been linked to Sandra Bullock, Famke Janssen, Kat Dennings, Olivia Wilde and Blake Lively.