"I hope people continue to be really sweet to her, and compassionate and respectful of her," Cyrus said exclusively to ABC News. "And just don't judge her and don't be too harsh on her. Because I'm not worried about her, it's everyone else that can be really hateful and harsh towards her."
She continued, "I want her to grow up and be able to really feel confident and not feel insecure about how anyone's ever made her feel."
But Miley thinks Noah has a pretty good grasp on fame thus far, with her debut single "Make Me (Cry)" hitting the Billboard top 100 late last year.
"Noah's cooooool. Noah's always busy!" she said of her little sis. "And I can't ever get a hold of her half the time and when I do … she's in EUROPE! She's everywhere, all the time! So it's really hard to actually get Noah in one room right now."
Miley has also been busy in the recording studio. Her new track "Malibu" dropped last week.
"I keep saying while promoting this new song ... that coming from Nashville I never would have imagined living in Malibu at this time in my life or by the ocean because I grew up on a farm," she said of the track's inspirations. "And now it's just sort of ironic that these two songs are same person, just (almost) 15 years later."
Cyrus' full interview with Radio Disney airs Wednesday at 2 p.m. on Radio Disney.
ABC News and Radio Disney are both part of parent company Disney.