The new unit, dubbed Mindshare SocialMedia8, will provide Mindshare's clients with a suite of social media marketing tools which can be integrated into the agency's existing media services, both traditional and digital.
The new entity will combine staff from each unit and Ciaran Norris has been hired to lead the new venture.
Norris previously worked as head of search and social marketing at Altogether Digital. His new title will be head of social marketing and he will report to Norm Johnson, Mindshare's global digital chief.
Johnston said: "SocialMedia8 accelerates our social marketing capabilities and enables us to help our clients capture and build earned media in a way that fully complements and integrates with their paid and owned media strategies -- both traditional and digital."
Igor Beuker, founder of SocialMedia8, said: "Video and social networking are impactful online trends across the globe.
"Even Oprah Winfrey, the Pope and Barack Obama are engaging millions of consumers with YouTube, Facebook, and Twitter, so brands feel the need to get their own social marketing strategy or consumer connectivity program".
Mindshare billings topped $23bn last year and has offices in 67 countries.
SocialMedia8 has previously worked with clients such as Nike, Nokia, LG and Heineken, with offices based out of Amsterdam, London and Milan.