The charity brought in Cake following a three-way competitive pitch. It will be V's retained agency for consumer work over the next year and will handle media for 'vinvolved', a new volunteering programme.
The body has given Cake a seven-figure budget to help it establish a culture of volunteering in 16- to 25-year-olds.
'V wants to operate as a lifestyle brand to radically change volunteering and what it means,' said marketing director Kathy McAllister. 'We are working with Cake to empower a generation with new opportunities to put their interests into positive action,' she added.
The programme, which the organisation claims is England's biggest ever youth action programme, was launched last week by indie band The Enemy. It has been given £75m in funding.
Cake associate director Davnet Doran will head up the account, leading a team of seven.
V is supported by the Office of the Third Sector, although it is an independent charity. It was set up in 2006 to implement a new framework for youth action and engagement in England put forward by the Russell Commission.
V handed a two-year retainer to Geronimo Communications in March 2007. But the agency's brief has now been changed to handle two projects for the charity.
'Geronimo is continuing to work with V on a regional and sector campaign and a skills debate that will take place in May,' said Geronimo director Anastasia Scott.
The charity is still using Iris for above-the-line work.