This marks the second time the 47-year-old actress has won the title.
The "Mother's Day" star told the mag that she was very humbled and "very, very flattered" when she was first told the news.
"I thought, 'Oh my god,'" she said. "There was this sort of very excited, teenage-y kind of moment."
Aniston told People that she feels most beautiful when she's healthy and strong. She also opened up about her insecurities, most notably, her derriere.
"I've never loved my butt," she said. "It's sort of a thing. I had a bubble butt and I was teased."
When asked how she would define beauty, she said, "Inner confidence. Peace. Kindness. Honesty. A life well-lived."
She continued, "Taking on challenges and not feeling shame for things that haven't gone the way you felt they should have. And not feeling like a failure or allowing people to critique your life and make you feel like you've failed at something. That's just toxic noise."
For more from Aniston's cover story, head to People.com.