Here’s a little twist that’ll make you feel old: When Season 3 premiered on July 4, 2019, Millie was already 15. That means by the time we were all watching her eat that cherry-flavored slushie at Starcourt Mall, she was a year older than her character. It’s like she outgrew the role in real-time, which is honestly kind of cool. She was literally growing up alongside Eleven, just with better hair and fewer psychic nosebleeds.
The funniest part? The show’s creators, the Duffer Brothers, had to constantly adjust the scripts because Millie’s voice was dropping. Yes, that’s right—she went through puberty on screen. In Season 1, she sounded like a tiny sprite. By Season 3, she had this deep, commanding tone that made her line “I’m going to kill you” sound genuinely terrifying. And she nailed it while being a 14-year-old with braces (yes, she wore braces during filming, which they cleverly hid with CGI).
Why This All Matters
You might be wondering, “Why does her age even matter?” Well, it matters because it makes her achievement even more insane. Imagine being 14, acting opposite actors twice your age, carrying a massive Netflix show, and doing it all while still figuring out your own homework schedule. That’s Millie. She was a kid playing a kid, and she crushed it. There’s no “child actor” weirdness here—she was just a total pro.
How Old Was Millie Bobby Brown In Season 3 | The Tube
It also makes the show feel more authentic. When Eleven gets jealous of Mike’s attention to Dustin, or when she giggles at the idea of getting a new dress, it doesn’t feel like a grown-up pretending. It feels like a real, awkward, beautiful teenager. And that’s thanks to Millie being exactly the right age to capture that energy. She didn’t have to “act” like a 14-year-old—she was one, just with a bigger paycheck and cooler special effects.
