The 'Once' singer will play an as-yet unnamed venue on September 28 in support of charity Oxfam. Presale tickets are available for the next 24 hours at £25.
"The location of the gig will be revealed just 72 hrs before the event so keep your ears and eyes open for more details," a statement on Vickers's website read.
Other acts performing at the show have been confirmed as Gabriella Cilmi and Pearl & The Puppets.
The first Oxjam festival took place in October 2006 and the event has since featured over 36,000 musicians playing at 3,000 nationwide events.
Vickers yesterday announced plans to release brand new track 'My Wicked Heart' as her third solo single on October 24. She also announced the re-release of her debut album Songs From The Tainted Cherry Tree on November 1.