Bishop Walkowiak was ordained to the priesthood June 9, 1979 by the late James Cardinal Hickey and was assigned as associate pastor to Saint Mary Parish in Lorain, Ohio. After his studies in canon law at The Catholic University of America, where he received the Licentiate degree in 1984 and the Doctorate degree in 1987, Bishop Anthony Pilla assigned him to the faculty of Saint Mary Seminary in Cleveland and also appointed him vice chancellor of the Diocese of Cleveland. In 1993, he began work as an adjutant judicial vicar for the appeals court of Cincinnati, Ohio; Steubenville, Ohio; and Washington, D.C. In 2006, Bishop Pilla appointed him pastor of Saint Joan of Arc Parish in Chagrin Falls, Ohio, where he served until June 2013. Pope Francis appointed him the 12th bishop of the Diocese of Grand Rapids on April 18, 2013, and he was ordained and installed as the 12th bishop of Grand Rapids on June 18, 2013.