Former EastEnders star Martine McCutcheon will stand in for Emma Bunton on her radio show while the ex-Spice Girl is on holiday.
The actress will go behind the microphone on The Saturday Show on Heart for the next two weeks.
She said: "I'm so excited to be joining Heart. I'm a genuine fan and listener of the station, so I'm really proud to be part of the team. I can't wait to get behind the mic, play some great tunes and a have a good laugh with the Heart audience."
McCutcheon, who was declared bankrupt earlier this year, shot to fame at the age of 18 as Tiffany in the BBC1 soap and went on to enjoy a number one hit with the song Perfect Moment and win a Laurence Olivier Award in 2002 for her role as Eliza Doolittle in the stage production of My Fair Lady.
She published a novel, The Mistress, in 2009, which was a top 10 best-seller, and starred with Hugh Grant in 2003 film Love Actually and more recently appeared in a series of TV adverts for Danone Activia yoghurt.
Global Radio's director of broadcasting Richard Park said: "Over the last year, Heart has introduced some of the UK's biggest celebrities to radio and it is testament to the strength of the brand that we can attract personalities of Martine's calibre to the network.
"I know that her great sense of humour and fun personality will be a hit with our listeners."