The agency will be tasked with creating a fresh brand identity, using a contemporary graffiti style, which will be rolled out in March on signage, menus and a poster campaign.
A CRM programme will also be developed to drive loyalty, while the website will be relaunched with the support of a viral campaign.
The Tiffinbites chain, named after the boxes used to pack home-cooked lunches for workers in India, comprises four restaurants in the City; a fifth outlet is set to open in the spring near St Paul's Cathedral.
Negotiations are also under way to secure distribution of Tiffinbites-branded products in high-street stores by the third quarter of the year, according to a company spokeswoman.
The first Tiffinbites outlet opened on Wardour Street four years ago.