Cook was born in Lehi, Utah and raised mostly in Arizona. He served an LDS Church mission in the Paraguay—Uruguay Mission of the church (with J. Thomas Fyans as his mission president) and is fluent in Spanish. Upon his return to the United States, he married Janelle Schlink in the Mesa Arizona Temple. He served as president of local seventies quorum. When his family was young he moved to Bountiful, Utah, where he worked for the church as secretary to the First Council of the Seventy.
At the age of 34, Cook became a member of the First Council of the Seventy. He served there for only one year, when he was transferred to the newly constituted First Quorum of the Seventy. He has since served as a mission president as well. He was given general authority emeritus status on October 6, 2007.
Cook has written books dealing mostly with families and faith and is a regular speaker at church schools. He and his wife are the parents of eight children and reside in Lehi, Utah.