'Twentysix Social Media' will offer a range of services covering every aspect of the online community, including strategy and brand planning, campaign set up and monitoring, asset creation and activity stream delivery and measurement.
The new division is led by Rachel Clarke, head of social media, who joined Twentysix after working for Diageo and JWT New York.
Clarke said: "Many public and private sector organisations need to know more about how to best connect with customers through social media, whether networking sites, interest groups or the many others ways of receiving and distributing content and information.
"Currently, very few get it right first time."
The Equality and Human Rights Commission is one of the first clients to use these new services and Twentysix is also working with Cancer Research UK's innovation team on an internal project.
Gail Dudleston, chief executive of Twentysix, said: "This is a really exciting development for Twentysix and complements our existing agency proposition.
"'Full service' means covering every possible angle of digital communications and social media is a vital part of that equation.
"A lot of clients and prospects have spoken with us about social media, underlining the need for a specialist division to handle it.
"We aim to deliver expert guidance across every part of the social media spectrum."