Cyrus captioned her selfie on Twitter, "Back in the yo! I am so f--king inspired right now," along with wave and blue butterfly emojis.
She's pictured in a white T-shirt with her hair in a ponytail sitting in front of a desk with sound equipment on it.
Carter, 31, and Cyrus ended their relationship after just over a month of dating.
"The Hills" star and musician hooked up in Italy just hours before the "Wrecking Ball" singer announced her separation from husband Liam Hemsworth in August — and just weeks after Carter and Brody Jenner ended their own relationship. Carter and Jenner were rumored to have been in an open marriage.
It was later revealed after Carter and Jenner split that they were never legally married despite having a wedding ceremony.
A source previously claimed that Cyrus' flagrant PDA with Carter put the final nail in the coffin for her and Hemsworth's eight-month marriage.
After Hemsworth filed, Cyrus released a new song titled "Slide Away," in which she seemingly sang about their relationship and why the couple didn't work out.
Fox News' Jessica Sager contributed to this report.