The 18-year-old singer has confessed she often sleeps in her parents' bed instead of her own, because she thinks there are monsters in her bedroom that she's "scared" of.
Billie spoke in a short teaser clip for her upcoming Apple TV+ documentary, 'Billie Eilish: The World's A Little Blurry, which was released on YouTube on Tuesday (Dec 15).
In the trailer, the bad guy hitmaker can be seen scrolling through her phone as she lays on a bed, and says: "This is my parents' bed. I sleep in here because I'm scared of monsters in my room."
Billie has opened up about her sleep struggles in the past, as she said earlier this year she finds it difficult to get to sleep, and is often plagued with severe nightmares when she does manage to drift off.
She explained: "I went to sleep on a plane sitting up the other day for, like, the first time ever. I've had sleep paralysis three times. I have a lot of weird sleep issues. I have these terrifying dreams and stuff. Sleep paralysis, night terrors…
"It takes me forever to fall asleep. I don't understand how people can fall asleep [straight away] - that's so weird to me."
The Bury A Friend hitmaker admitted her bad dreams can impact on her whole day, and it's been particularly tough lately thanks to a recurring nightmare.
She added: "It's weird because normally the nightmares I have don't make me wake up. Lately, I've had a couple that do, but normally the dream is the whole night - so the whole night is terrifying. They can really mess me up, so the whole day is off sometimes.
"I'll have a dream that really screws with my head and makes me kind of just feel... I don't know what it is but it makes me feel uncomfortable all day. I've had the same nightmare for like two months in a row. Horrible. And it affects me day-to-day. It affects how I act and all that."