Johnson taught at Union Theological Seminary in 1891, Princeton Theological Seminary from 1894 to 1897, and Danville Seminary (where he taught New Testament literature and exegesis) and Centre College of Kentucky (logic and psychology) from 1897 to 1901. From September 1903 he was Professor of Greek and New Testament Literature at Lincoln University, also serving as dean of the faculty for several years. In 1914, he received a doctorate of divinity from Centre College.
