"The people I find most beautiful are the ones who aren't trying," the actress told the mag, swearing she'd laughed when she found out she was this year's cover girl, declaring the decision "ridiculous."
"I've told no one," she said.
At 50, she's the oldest celebrity to be featured on the magazine's annual cover celebrating beauty -- a factoid that likely wouldn't register with her 5-year-old son.
"[H]e asked why I have wrinkles, and I said, 'Well, I hope some of them are from laughing so much.' And he touched my face and said, 'You're not old, you're just happy.'"
As Bullock talks about being a mom to the boy she adopted in January 2010, a kid she says doesn't know what she does for work but thought she was an astronaut for a while, the global star sounds more and more like a person who'd be cool to hang out with.
"Real beauty is quiet," she said. "Especially in this town, it's just so hard not to say, 'Oh, I need to look like that.'
"No, be a good person, be a good mom, do a good job with the lunch, let someone cut in front of you who looks like they're in a bigger hurry."
The list, which has included three men since its 1990 debut, became ladies-only territory in 2006.