The London office will launch with founding client Costa, following a pitch in November last year.
The agency was set up in Sydney in 2007 by British expats Kat Thomas and Anthony Freedman, and has a client roster that includes Virgin Mobile, Toyota, Unilever, Mondelez, Nike, Google and Westfield. Havas Worldwide became majority shareholders of the business in 2011.
The London office, based in Clerkenwell, will be headed by the agency's managing director Matt Buchanan who has relocated from Sydney. He will be supported initially by a team of five, with further hires anticipated. Thomas will take on a global role.
Before moving to Australia in 2010, Buchanan worked in London for more than ten years, holding senior positions at The Red Consultancy and Bell Pottinger.
Buchanan told PRWeek that opening in London was a natural progression as part of a long-term strategy to grow internationally.
"We know the London market well and the opportunity came up to pitch for Costa in the UK," said Buchanan.
"The success One Green Bean has enjoyed in Australia is indicative of the changing demands of clients, and their increased focus on owned and earned channels. I’m thrilled to be bringing our proposition to the UK market."
Thomas added: "Marketers are savvy enough to know great creative thinking can come from anywhere. It’s an ideas economy and our business is built around delivering provocative, memorable work."