Monahan joined the leadership team of CEB (formerly the Corporate Executive Board) in 1996. He was named its chief executive in 2005 and chairman in 2008. He presided over an expansion of revenue, which increased 157% from 2005 to 2016. During his term, CEB acquired Evanta Ventures, a Portland-based best practice insight and technology company.  CEB was acquired by Gartner in 2017 for $2.6 billion. He stepped down from CEB Inc. in June 2017.
