Amy will appear in the fourth series of the late-night edition of the soap set in Ibiza, where she will play the latest member of the McQueen family.
"My younger sister is just about to go into Hollyoaks in September - the late night version, the X-rated version," she said on Daybreak.
"I'm a bit worried actually. I don't know if my brother will be watching that!"
The series will air on E4 in September, and will feature the likes of Rachel Shelton (Mitzeee Minniver), Jennifer Metcalfe (Mercedes Fisher) and Jorgie Porter (Theresa McQueen).
Speaking about the rumoured Girls Aloud reunion, Kimberley said: "I think the ten-year anniversary is a massive thing and we're all really excited about it, so I think there definitely will be some plans put in place for that, which is really exciting.
"I think we'll probably have more to see in the New Year, but we are chatting about it now and it is a nice thought."
The singer also paid tribute to Amy Winehouse, saying: "'I just feel like it's such a loss - musically as well. She's so talented and everybody has so much respect for her."
Kimberley had previously spoken of her excitement upon hearing about her sister Amy's Hollyoaks Later role.