The agency won the business after a five-way pitch, which kicked off in August.
Albion London was the previous incumbent on the account. It had worked with the brand for the past three years, but declined to repitch.
Nicola Pearson, the commercial director of Cafédirect, made the appointment. Brothers and Sisters will now develop a long-term strategy for the brand to showcase the high-quality taste of the company's products.
An integrated campaign will launch next year to help the brand grow its market share as it looks to combat increasing competition from supermarket own-label Fairtrade tea and coffee products.
Juliet Haygarth, the Brothers and Sisters managing director, said: "Cafédirect has an interesting heritage and business model that sets it apart from the rest of the sector."