Bednar was sustained as a member of the Quorum of the Twelve on October 2, 2004, the youngest man named to that body since Dallin H. Oaks in 1984. He was ordained an apostle on October 7, 2004 by Church President Gordon B. Hinckley. Bednar and Dieter F. Uchtdorf were called to fill the vacancies created by the July 2004 deaths of quorum members David B. Haight and Neal A. Maxwell. As a member of the Quorum of the Twelve, Bednar is accepted by the church as a prophet, seer, and revelator. In addition, Bednar is a member of the Church Board of Education, the governing body of the Church Educational System. He is also the youngest member of the Quorum of the Twelve Apostles at this time.
From 1980 to 1984, Bednar was the assistant professor of management in the College of Business Administration at the University of Arkansas in Fayetteville, Arkansas. He became assistant professor of management at Texas Tech University from 1984 to 1986. He then moved back to the University of Arkansas as the Associate Dean for Graduate Studies in the College of Business Administration from 1987 to 1992 and was then the director of the Management Decision-Making Lab from 1992 to 1997. In 1994, he was recognized as the outstanding teacher at the University of Arkansas and received the Burlington Northern Foundation Award for Excellence in Teaching. He has twice been the recipient of the Outstanding Teacher Award in the College of Business Administration.
Bednar then served as the president of Ricks College/Brigham Young University–Idaho from 1997 to 2004 in Rexburg, Idaho. There, he oversaw and managed the transition of the school from, what was at the time, the largest private junior college in the United States, Ricks College, to a four year university, Brigham Young University-Idaho.