The adorable British starlet has been rocking shorter locks ever since initially shaving her hair for her role as Eleven on Stranger Things, but she stepped out for the season two premiere party in Los Angeles on Thursday night with shoulder-length, sleekly flat-ironed brunette locks.
"I wanted to do something different," Brown explained to ET's Leanne Aguilera. "My amazing hair stylist, Blake, he's so incredible and I feel like we wanted to do something crazy and creative, and I feel like we accomplished that."
Not only did she rock extensions in her center-parted bob, but her outfit was noticeably mature, too.
The 13-year-old actress looked fierce in a black leather shirt dress and white patent leather kitten heels, both from Calvin Klein's Raf Simons-designed 205W39NYC imprint. She finished her look with an icy, silvery eye and lightly berry-stained lips.
She also shared a laugh with her fellow Stranger Things co-stars -- Caleb McLaughlin, Noah Schnapp, Gaten Matarazzo and Finn Wolfhard -- on the red carpet. After the event, she even posted a close-up of just her and Wolfhard on Instagram, along with a sweet caption.
"@finnwolfhardofficial I’m so blessed to have a great (on screen romance) with this lovely boy! Eleven loves you," she wrote, adding a star emoji.
Brown's hair isn't just a story in real life -- she's got brand new locks on the Netflix hit as well.
"I think that Eleven's hair storyline goes really funny, and it's a very funny storyline," she told ET of the curly hair her character has in season two. "We're very excited for it."
Eleven also has a lot more nosebleeds this season, and she joked that it definitely "gets messy." "I feel like Eleven just channels some anger," she said of why we'll be seeing so much more of the drips.