Fitzgerald will report to the agency’s executive creative director, Ali Alvarez, and work across its client portfolio, which includes Jaguar Land Rover, BSkyB and Tate.
He has been at GS&P since January 2011, having previously worked at the Australian agencies Three Drunk Monkeys and Belgiovane Williams Mackay.
Fitzgerald has worked on brands including Chevrolet, Adobe, BBC Knowledge and Virgin. He has won one bronze Lion at the Cannes Lions International Festival of Creativity.
Alvarez said: "It’s taken a long time to find a writer who has the perfect ratio of funny to smart to innovative to all-round awesomeness."
Other creative hires at The Brooklyn Brothers include Will Bingham and Victoria Daltrey, who are joining from Colenso BBDO.Follow @Jezzalee