Before becoming president of Princeton, Barnes was a chaired professor at Pittsburgh Theological Seminary while also serving as the pastor and head of staff of Shadyside Presbyterian Church. He previously served pastorates in Madison, Wisconsin, and at the National Presbyterian Church in Washington, DC. He is a frequent lecturer and preacher at conferences, academic gatherings, and in congregations across the country. He is the author of eight books and serves as a columnist for The Christian Century.
His writing and academic work reflect his deep commitment to the theological formation of pastors to lead the church in changing times.