The media personality took to Instagram to tell those closest to her about the sad news.
Posting a beautiful black and white flashback photo of her dad, split with a shot of the pair holding hands in what appeared to be a hospital bed - Karl Stefanovic's ex-wife paid tribute to her father: Max Thorburn.
"A journalism career spanning over 50 years in TV, newspapers and radio," the post read.
"A role model to many and my biggest supporter. Thank you for being the beloved poppy to my children and my Dad. Max Thorburn 27/4/1946 - 18/10/2018"
Cassandra told the Daily Mail, "My dad’s passing is a loss to so many. I was just blessed to be his daughter and my children had the most incredibly devoted poppy."
"What more can be said? He fought hard for 3 years and the last six months have been excruciating. We are devastated."
Adding, "My dad taught me to accept life is full of imperfect people, including ourselves and to approach each day as an opportunity to do better. If you hurt someone be man enough to admit it and make amends. True gifts."