Cooper joins from Archibald Ingall Stretton, where he was the lead planner on the O2 Business and Corporate accounts.
He will work across all of Geronimo's clients, which include Direct Line, Direct Line for Business, ING Direct, Seat Automotive, Seat Fleet, Sara Lee, GlaxoSmithKline and BBC Worldwide.
Andy Snuggs, managing director at Geronimo, said: "In this tough climate you need to invest in order to grow.
"We're working with our clients differently to create value for them and their customers, and great strategic planning is at the core of this.
"Scott's CV speaks for itself and with his finance and B2B experience he'll fit right in at Geronimo."