The 32-year-old Gossip Girl star shocked everyone back in April when she took to Instagram to reveal she was "having a blonde moment" in a selfie.
But overnight, celebrity hairstylist Justin Anderson, who has previously worked with Aussie bombshell Margot Robbie, revealed Meester's new lob and dark hue.
Though we've come to know her as a sassy, Upper East Side brunette, Meester is actually a natural blonde.
"Leighton was a blonde when she came in to read, but Blake [Lively] was the blonde, so we asked her to colour her hair,” Gossip Girl creator Josh Schwartz previously told The Hollywood Reporter.
“A risky move on her part in the middle of pilot season, but she did a sink-rinse dye job to audition as a brunette.”