The 19-year-old actress also shared a topless back selfie.
Bella Thorne and Tyler Posey have only been together a month or two, and already they're sharing clothes.
The 19-year-old actress posted a sexy pic to Snapchat on Sunday of her posing in nothing but a robe, sneakers, a lacy peach bra and her boyfriend's underwear. "His boxers," she captioned the snap.
WATCH: Bella Thorne Confirms She's Bisexual to Fans on Twitter
This wasn't the only scantily clad photo that Thorne shared over the weekend. She also posted a topless photo of herself that revealed a huge tattoo of angel wings on her back. The ink is probably temporary as she did not have the tat in the bikini-clad pic she recently posted of herself on top of Posey.
Last week, Thorne explained to ET why it's important to express herself on social media. "I'm, like, an open book," she said. "But that's what I think that my fans enjoy about me the most, is that they feel like they really know me. And they do, they really f**king know me."
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As for whether she's ever crossed the line with her posts, Thorne quipped, "I guess I haven't learned the line of 'too far' yet, because I always do pooping snaps. People always get after me about my pooping snaps. You know what I tell them? ...I don't give a f**k!"
The Famously in Love star is also helping Posey get acclimated to tweeting, snapping and Instagramming. "He doesn't [post] a lot on social media, so it's been… that's like the only thing that's been interesting is [that] I'm so about the socials and he isn't," she said of the 24-year-old Teen Wolf star. "It's a little bit of like, teaching and learning and pushing and pulling."
WATCH: Bella Thorne Straddles Tyler Posey in Racy Bikini Shot, Calls Him Her ‘Man Crush Everyday’