The 54-year-old comedienne has admitted she has some "very, very large shoes to fill" when she replaces the 81-year-old star – who died in September while undergoing a minor throat procedure – but is determined to adopt the former presenter's no-nonsense attitude when it comes to her comments.
Speaking on 'Jimmy Kimmel Live!', she said: "In her honor, I will not be holding back. I am giving no passes, I am going to let people have it, I'm gonna bring the hammer down.
"This was a job that was held by our dear friend Joan Rivers. I understand I have some very, very large shoes to fill."
Kathy then decided to practice her tough-love approach discussing the fashion choices of celebrities on the programme by testing out her tactics on Jimmy.
She told him: "You might want to up your game. I'm tired of the same suit every time. I get it. It's Gucci, it fits well - yawn!
"Give me some sparkle! Give me a fig leaf! Take a risk for god's sake. Don't just show up again looking nice-ish. Give me something."
Kathy will take over from Joan - who hosted the show since its first episode in September 2010 - on January 12, 2015 and will front 17 new episodes alongside fellow newcomer Brad Goreski and returning panelists Giuliana Rancic and Kelly Osbourne.