"A long time ago this 17 year old girl with the questionable hair style, encouraged by her Mum tried her hand at modelling [sic]," she wrote in the caption.
"She was generally a bit shy, had little self confidence and was just your average teenage girl."
Rebecca went on: "She also thought she was overweight and had bad skin. ( Like seriously dude - you had it soooo good)."
She completed the post with the hashtags: #the80's, thesimplelife, #withquestionablehair, #butnoiphonestorecordyourstuffups, #thebenefitofhindsight , #lovethelifeyoulive and #atseventeen
Gibney starred in Packed to the Rafters from 2008-2013. Photo / Supplied
Later she posted an image with hashtags #theteenageyears" and #somewouldsaybogan" showing her riding a quad bike, saying: "Rocking my flannie. At least it matches the bike!"
It's not the first time the Flying Doctors star has spoken about the crippling self-doubt she experienced as an adolescent.
Speaking to The Australian Women's Weekly recently, Rebecca confessed: "I spent a lot of my 20s self-sabotaging and making mistakes and I ruined relationships."
Rebecca starred alongside Peter O'Brien in the 80s drama The Flying Doctors. Photo / via Instagram
"I kept [thinking], 'Oh I'll be dried up in a few years of they'll find out I'm faking it'.
She added: "That would be the biggest advice I would give any young woman: remember you are unique and there is no one else like you - believe in yourself and manifest whatever it is that you want."
The blonde beauty went on to build a successful acting career spanning four decades.
In 2009, she won a Gold Logie for Most Popular Actress, for her role in Packed to the Rafters.
Gibney is currently in her native New Zealand filming Channel Seven drama Wanted.
