The new account was awarded following a competitive pitch, and it will be overseen from CitySavvy’s New York, London and Amsterdam offices.
Zettabox was set up in June by James Kinsella, the technology industry veteran and entrepreneur.
Based in London and Prague, Zettabox is billed as the first pan-European cloud-based storing and sharing platform that will fully comply with all upcoming EU data privacy regulations that restrict what kind of data can be stored.
Under the new regulations, global firms with European customers face fines of up to five per cent of total revenue if they fail to comply with the data controls.
Kinsella said: "CitySavvy has provided excellent strategic advice to us along with top-notch execution for our European launch."
London-based CitySavvy opened its New York office one year ago.