Born and raised in rural western Oklahoma, Bishop Mueggenborg graduated from Oklahoma State University in 1984 with a geology degree and a related computer science degree. He attended the pre-theology program at St. Meinrad Seminary in Indiana and the theology program at the Pontifical North American College in Rome. He was ordained a priest for the Diocese of Tulsa in 1989.

Bishop Mueggenborg completed a Licentiate degree in Biblical Theology from the Pontifical Gregorian University in Rome in 1990. During his 30+ years as a priest, Bishop Mueggenborg has served as parochial vicar and pastor in several parishes and in a variety of ministerial roles, including high school chaplain and teacher, Newman Center chaplain, Director of Clergy and Education, and Vicar for Religious.  He also served on the administrative staff of the Pontifical North American College and was adjunct professor at the Gregorian University. Pope Francis appointed him Auxiliary Bishop of Seattle on April 6, 2017, and he was ordained bishop on May 31, 2017.

Bishop Mueggenborg comes from a farming and ranching family and enjoys mountain biking and hiking in his free time. He has climbed Mt. Kilimanjaro and has hiked the Grand Canyon as well as a substantial portion of the Camino de Santiago. He credits his love for the outdoors to his rural upbringing and his involvement in the Boy Scouts of America.