The 28-year-old - who relaunched her pop career late last year after opting out of the spotlight for a number of years - is stepping in for Dermot O'Leary to host his regular weekend show.
She has recorded a three-hour show to be broadcast this Saturday as she gears up for the release of her third album Sheezus.
Allen said: "I've been a guest on Dermot's show loads of times, and I've been secretly plotting to take his place, so am very pleased I will have the studio all to myself."
Earlier this week the singer showed some disarming honesty when she conceded recent singles were not up to scratch, blaming her record label and radio stations for not wanting to air her "better" songs.
She responded to a Twitter user who said her new material was "docile pop rubbish", by saying: "What you've heard so far yes. All I can do is do my best, the labels and the radio stations won't play the better stuff."
Allen's Radio 2 show - to be broadcast at 3pm - sees her joined by columnist and author Caitlin Moran, Vogue editor Alexandra Shulman and Newsnight's Kirsty Wark.
It is not her first experience as a presenter - she also hosted a short-lived chat show for BBC3.