Iain Jacob, chief executive of Starcom MediaVest Group, said: "GlaxoSmithKline has strong ambitions in the region as we do and we are excited about the opportunity that its rapid expansion represents."
GSK manufactures a wide number of consumer products including Aquafresh toothpaste, Beechams powders and soft drinks Lucozade and Ribena.
This is the first time that Starcom MediaVest Group has been appointed to the GSK roster.
The agency has been appointed to the business in: Russia; the Ukraine; Poland; the Czech and Slovak Republics; Hungary; Romania and Bulgaria; Latvia; Lithuania and Estonia; Slovenia; Croatia; Bosnia-Herzegovina and Serbia.
Paul Valdez, regional marketing director for GSK, said: "Central and Eastern Europe is a fast-growing business for GSK and we are determined to make the most of the opportunities there. Starcom MediaVest is a strong player in the region and will be an excellent partner for us."
Jacob was also instrumental in the agency being awarded the £13m pan-European Del Monte brief last year. Starcom MediaVest took the business from the incumbent Brand Connection in the UK and Initiative across the continent. The agency also took the £10m brief for Revlon across Europe during 2006.