The 17-year-old showed off significantly lighter locks in a selfie posted Sunday night on Instagram.
Captioning the photo with a sleepy-face emoji and a few "zzz's," the "Keeping Up with the Kardashians" star didn't offer many clues to her new look.
In the past, she has fooled fans into thinking she had lightened her natural brunette hue.
Last February, she tweeted a picture of herself with a new blonde 'do and the caption " New look….? What do u think? Lol!"
When fans questioned her new look, Jenner came clean.
"Don't worry! Still a brunette! #fooledyou #sillyme," she wrote, posting a picture of herself with her usual dark locks.
Meanwhile, Jenner's older sister Kim Kardashian has been showing off a honey hue since becoming mother to North West.