The former SM:TV Live presenter will appear on the sofa for three days next week, beginning on Monday 13 November.
Cat – who rose to fame alongside Ant and Dec on Saturday morning kids TV in the late 90s – will be joined by Rylan Clark on Monday and Tuesday, before Craig Doyle hosts alongside her on Wednesday, HuffPost UK understands.
The Sun was first to report news of Cat joining the on-air team of the ITV daytime show, with an unnamed source telling the publication that if her stint “goes well she could be a much more permanent solution to Holly leaving”.
Last month, Holly announced she would exit This Morning with immediate effect in a statement posted on her social media accounts. This followed the news a week earlier that a man has been charged over an alleged plot to kidnap her.
She said it was “such a difficult goodbye” after 14 years on the sofa, adding: “I now feel I have to make this decision for me and my family. I will miss you all so much.”
A week later, he then resigned from ITV altogether after admitting to having lied to producers about an affair with a younger colleague on the show.
In the months since, Holly had continued to front This Morning with a rotating roster of the show’s existing presenters, including Alison Hammond, Dermot O’Leary, Craig Doyle and Josie Gibson, who all rallied round Holly on social media after she announced her exit.
Holly joined This Morning in 2009 alongside Phillip as a replacement for former co-host Fern Britton.
Other names who are rumoured to be in the running to replace Holly on a permanent basis include Good Morning Britain host Kate Garraway, former Big Brother presenter Davina McCall and Strictly Come Dancing champ Abbey Clancey.
This Morning airs weekdays at 10am on ITV1.