The former 'Daybreak' presenter will stand in for Holly's regular co-host Phillip Schofield for two days in March, as he films the new series of 'All Star Mr & Mrs'.
Christine has regularly stood in for Holly during her absences from the show, hosting alongside Phillip, with whom she presents 'Dancing On Ice'. However, it will be the first time the two women have fronted the show together.
Adam Vandermark, editor of the ITV daytime show, said: "Holly and Christine will make a great new hosting combination - their friendship and love of the show will be reflected I'm sure.
"'This Morning' hasn't had an all-female hosting duo for quite a while, so it'll bring a fresh and fun few days for our viewers."
Despite rumours of rivalry between the two women after Christine took over Holly's role on 'Dancing On Ice' in 2012, the pair are actually close friends, and are regularly pictured out partying together.
Christine will take to the sofa with Holly on Monday 17 and Tuesday 18 March.