The brief, which will be for 12 months initially, is to help Zopa expand its reach to the mass-market financial sector and position it as an alternative to the major banks.
Consumer-facing and digital activity will look to communicate Zopa's rates to borrowers and savers. Brands2Life will seek to expand coverage from personal finance media to broader consumer lifestyle titles.
Public affairs work will target opinion formers in Whitehall to help them understand the place that Zopa has within wider discussions on the banking and financial industries. It will also aim to show what the lending service can do for the UK economy.
Peer-to-peer lenders' activities have historically not been regulated, but will come under the scope of the Financial Conduct Authority from April 2014.
Zopa facilitates borrowing and lending directly between its members, which it claims reduces costs. It has about 500,000 members, who have exchanged more than £292m since Zopa launched in 2005.
The company has worked previously with agencies including Bite and Financial Dynamics (now FTI Consulting), but is believed not to have had one in place before appointing Brands2Life following a pitch.
Brands2Life engagement director Scot Devine said: 'Zopa is one of the most innovative brands we have seen.
'Finance is stuck in the UK, but the country is ready for a good-news financial story.
'Our integrated campaign, working across multiple channels with a single-minded focus, will show how Zopa can get Britain's money moving again.'