Cyrus debuted a new short hairdo earlier this month, a decision which has faced criticism from many of the star's fans.
Jackson, who is the daughter of the late Michael Jackson, voiced her approval of Cyrus' new look on the social networking site and praised the Hannah Montana actress's originality.
"I don't know why people keep hating on Miley's new cut... I love it!" the 14-year-old wrote. "She's being herself and she's being different and I love her for that!"
Cyrus has revealed that her fiancé Liam Hemsworth loves her new haircut and that his opinion is one of the only ones that matters to her.
She has said that her new style has made her feel more "free" than she ever has in her life.