"He has been an angel in my life for many reasons," Woodley, who played Clooney's daughter in The Descendants, tells Vanity Fair for its July cover story. "He knew everyone's name on set. He treated everyone as an equal and everyone got his warmth."
Warmth is also a word that has been associated with Woodley, 22, who is earning rave reviews for her role in The Fault in Our Stars, in which she plays a teenager battling cancer. And like her mentor, she's also deeply concerned about the world around her – even if she's not quite sure how she can best help.
"As much as this industry is a platform for talking about big issues, there's also so many f----n' issues," she says. "Maybe the only thing that I'm supposed to do is just show up and be me in every moment. Because I do feel like one of my gifts is to be open and lovely – simple things like smiling at strangers and having kind, small interactions. I think that is what's going to ultimately shift things."
One person who isn't worried about her figuring it all out? Clooney himself. The engaged Oscar winner only has words of praise for the young star.
"Shailene can do whatever she wants," he says. "If she wants to be a movie star, she has it. If she wants to change the world, she will. Her talent and kindness go hand in hand."
"We'll be talking about Shailene Woodley 40 years from now," he adds. "I've never seen anyone so young that has so much together."