Emma B will start the 2pm to 6pm programme on March 27, joining the likes of Pat Sharp, Lynn Parsons and Pete Waterman on the easy-listening station.
She spent eight years at Radio 1, winning four Sony Radio Awards for her Sunday Surgery show with Dr Mark Hamilton. After leaving Radio 1 in 2005, Emma B joined London's Heart 106.2, where she became the first ever solo female to have the number one drivetime show in the capital. She has also worked at Radio 5 Live, LBC and BBC 6 Music.
Andy Carter, Smooth Radio brand managing director, said: "Smooth's audience is growing fast across the UK. One compelling reason for this is that its listeners are able to tune in to listen to some of Britain's best loved presenters playing their favourite music at whatever time of the week they choose. Emma's weekend show will have a relaxed feel, perfect for Sunday afternoons."
Emma B added: "After having a year or so off being a mum, I'm absolutely thrilled to be back on the radio and to be in the company of a collection of such first-rate broadcasters at Smooth Radio is a real privilege."
GMG has also announced that David Jenson will present a regular Sunday afternoon show on Smooth Radio between 6pm and 8pm, starting on April 4. The Double Top 20 programme will involve Jenson playing the top 20 songs from a particular week in a particular year.
In October 2010, Smooth Radio expanded to a national station available on a number of platforms, including DAB and Freesat. According to audience research data for the fourth quarter of last year, the UK-wide station attracted 3.08 million listeners a week.