The agency will provide the charity with strategic comms consultancy on a number of its key projects over the next year.
English PEN promotes and defends the freedom to read and write, in the UK and around the world, by campaigning for free speech and creating opportunities for expression in socially excluded communities.
As part of the new relationship, the agency will continue to promote the PEN Pinter Prize and support the annual PEN Quiz, working on a pro bono basis.
Dotti Irving, chief executive of Four Colman Getty, said: "Four Colman Getty is a company specialising in both campaigning and culture. English PEN is a perfect match for us."