David H. Yarn Jr. spent over four decades at what he called "the BYU." After earning his undergraduate from the university and studying at Columbia University for his masters and doctorate degrees, he returned to BYU to serve as a professor in the Department of Philosophy and later as the first dean of Religious Instruction. He was a recipient of the Karl G. Maeser Distinguished Teaching Award. He delighted in teaching and bearing solemn witness of the ministry and mission of the Savior, whether in the classroom, at church, or at home. 

After retiring from full-time teaching at BYU, he worked as a sealer in the Provo Utah Temple and later as president of the Atlanta Georgia Temple from 1986 to 1989. He also served as the general editor of the J. Reuben Clark Papers project at BYU.

David H. Yarn was married to Marilyn Stevenson for sixty-six years. They were the parents of six daughters, the grandparents of twenty-two grandchildren, and the great-grandparents of twenty-eight great-grandchildren.

He died of natural causes at his home in Provo in 2012 at the age of ninety-one.