The contract, awarded following a professional brief, includes G4S's security solutions, global energy and mining operations, and encompasses both digital and social activity alondside media engagement.
The account will be led by Fishburn’s chief operations officer Leah Katz, who said: "We are delighted to be working with G4S to support such integral parts of their business. The company is one of the most prolific employers in the UK and provides a number of indispensable services around the world.
"What’s more, as an agency Fishburn is dedicated to doing impactful work that makes a real difference to clients and G4S is a welcome addition to our roster."
Nigel Fairbrass, director of media at G4S, added: "This brief is all about supporting our business units and making a clear, positive impact towards their bottom line. Fishburn showed that as an agency they have the credentials and experience necessary to help us achieve that. We will be working with them on an ongoing basis and are confident that they have what it takes."
G4S handles much of its PR through its in-house team, but has also previously worked with RLM Finsbury.