Following his graduation from Concordia Seminary in 1963, Feuerhahn was a missionary at-large in Wales and England until 1967 for the Evangelical Lutheran Church of England (ELCE). He also served two congregations — St. James Lutheran Church, Cardiff, Wales (1967-70) and Resurrection Lutheran Church, Cambridge, England (1970-77). From 1977 until joining the St. Louis seminary faculty in 1986, he was preceptor (president) of Westfield House, the theological-training college of the ELCE, in Cambridge.

In the years 1975-85, Feuerhahn held office in the ELCE as a pastoral counselor and vice-chairman of the church body. He also served as chairman of the Lutheran Free Conference of Great Britain (1981-85). He was a visiting professor on two different occasions (1998-99) in Yekaterinburg, Russia.

For the Missouri Synod, Feuerhahn served on the LCMS Commission for Doctrinal Review (1993-99) and the LCMS Commission on Worship (1995-2001), and was on a panel for discussions between the LCMS and the Evangelical Lutheran Church in America (1999-2000).

In addition to his Master of Divinity degree from Concordia Seminary, St. Louis (1963), he earned a bachelor’s degree in history at Concordia Senior College, Fort Wayne, Ind. (1959) as well as Master of Philosophy (1980) and Doctor of Philosophy (1992) degrees from Cambridge University in England.

His theological and academic work focused on modern church history, the 20th-century ecumenical movement and particularly the theology and work of Hermann Sasse. He was the author of numerous published articles on Sasse and edited several collections of Sasse’s essays. He also produced the definitive bibliography of Sasse’s writings. A festschrift titled Lord Jesus Christ, Will You Not Stay was published in Feuerhahn’s honor in 2002.