In 2012, Brian was appointed as the Commissioner of the Chicago Public Library. In a press releasing announcing his appointment, Chicago Mayor Rahm Emanuel said, “Brian Bannon has the experience and vision to lead the Chicago Public Library and guide its expansion in the digital world,” and “it is more important than ever that our libraries provide children, students and families with resources to learn and grow. With his expertise in digital technology, Brian will expand the online resources of the Chicago Public Library and broaden the horizons of those who rely on it.”

In 2017, he was named a Henry Crown Fellow at the Aspen Institute, an educational and policy studies organization. The fellowship is aimed at mobilizing leaders under age 45 to tackle the world's most intractable problems.

Previously, Brian was the Chief Information Officer for the San Francisco Public Library, responsible for its digital strategy, information technology, web media, and online services. Brian also worked as the chief of branches, managed the staff and operations for San Francisco's neighborhood libraries, and had a central role in implementing San Francisco's $200 million branch library improvement program.