The Spice Girl, who has been a patron of the charity for 12 years, will play a career-spanning set of hits together with the live debut of new song 'Phenomenal Woman'.
"I'm so excited, what an honour to be performing at the Breast Cancer Care fashion show," Halliwell said.
Halliwell's last solo album was 2005's Passion, which charted at number 41 in the UK. Its two predecessors had reached the top five.
The singer is tipped to release her fourth solo record, rumoured to be called Putting On The Bling, either this year or in 2013.
The Breast Cancer Care fashion show features 24 men and women who have been affected by breast cancer on the catwalk.
Styled by Hilary Alexander and London Fashion Week coordinator Lesley Goring, the models will wear outfits from the high street and designers including Alexander McQueen, Stella McCartney and Vivienne Westwood.
The event takes place at Grosvenor House, A JW Marriott Hotel on Park Lane and tickets are priced at £69-£185, which includes a champagne reception, dinner, catwalk show and evening entertainment.
Watch the Geri Halliwell 'Look At Me' music video below: