Her brief will be to generate new business and oversee planning for pitches and client campaigns.
She will report to Geronimo founder and MD Karen Harris, who said the role had been created to accommodate growing business at the 41-strong agency.
At Biss Lancaster, Sarah Harris sat in the consumer team but worked on planning and strategy for its corporate and healthcare divisions. She left last week and joins Geronimo in January.
Karen Harris said: ‘We wanted someone senior who was experienced in planning rather than someone who would get consumed with new business once it got through the door.’
The agency’s recent work includes a campaign for the Department for Education and Skills that encouraged 16-year-olds to remain in education. Its clients in the voluntary sector include education charity The Edge.
Separately, Geronimo is in talks with sister Tribal Group companies Tribal MPC and Atlas Media Group over ‘future integration’. Karen Harris said: ‘Tribal MPC concentrates on local government, Atlas on healthcare, and us primarily on education, so we complement each other.’
Harris added that the talks were in ‘very early stages’.
Geronimo is to relocate from North London to Oxford Street next April.