Barry was acting director of the Institute of Governance, Public Policy and Social Research at Queen's University Belfast and is currently Reader in Politics in the School of Politics, International Studies and Philosophy and assistant director of the Institute for a Sustainable World.

From January 2007 to June 2007, Barry was the "Benedict Distinguished Visiting Professor of Political Science" at Carleton College in Northfield, Minnesota.

Barry's political life began in the Workers' Party and then Democratic Left.

By January 2003, he was elected as joint leader of the Green Party in Northern Ireland, alongside Kelly Andrews.

He was a prime mover behind the creation of an all-island Green Party,[4][7] officially launched in December 2006 in advance of the 2007 NI Assembly elections, which saw the Greens get their first Assembly seat in North Down with Brian Wilson.