He moved back to the States to attend the University of Washington and transferred to Brigham Young University in 1996 after a two-year Mormon mission in Madrid, Spain. At BYU, he double-majored in English and computer science, and graduated in 2000 alongside his fiancée Mindy, whom he married that fall.
While at BYU, Ken captained the university's successful quiz bowl team, and began writing and editing questions for National Academic Quiz Tournaments, a company that organizes quiz competitions attended by hundreds of colleges and thousands of high schools nationwide. Ken also began to notice a parade of his friends and acquaintances from the world of quiz bowl appearing on game shows like Who Wants to Be a Millionaire, where many were able to pay off their student loans and buy flashy sports cars. With this in mind, Ken began to revive his childhood dream of appearing on Jeopardy!
Ken was working as a software engineer for a Salt Lake City health care staffing company in 2004 when he got the phone call telling him that his contestant audition had been successful and he would appear on Jeopardy! that June. He spent a month making flash cards and cramming on familiar Jeopardy! subjects like U.S. presidents, world capitals, and "potent potables" (Ken doesn't drink).
Much to his surprise, Ken's Jeopardy! appearance extended far beyond a single game: he took advantage of a recent rule change allowing returning champs to appear on the show indefinitely, and spent the next six months hogging America's TV screens. Before losing on the November 30 show because he didn't know enough trivia about H&R Block, Ken won 74 games and $2.52 million, both American game show records.
After his Jeopardy! streak ended, Ken became a best-selling author. His books include Brainiac, about the phenomenon of trivia in American culture, Ken Jennings's Trivia Almanac, the biggest American trivia book ever assembled, Maphead, about his lifelong love of geography, and Because I Said So!, debunking parenting cliches. For children, he wrote a series of Junior Genius Guides full of fun projects and amazing facts.
Ken co-hosts the podcast Omnibus, explaining forgotten corners of human history and culture to posterity, and speaks at college campus and corporate events on topics ranging from the importance of learning to the future of artficial intelligence (drawing on his 2011 Jeopardy! loss to IBM's supercomputer Watson).
In 2020 Ken was named Jeopardy!'s "Greatest of All Time" after winning a prime-time competition against James Holzhauer and Brad Rutter. Later that year, he returned to the show to fill in for longtime host Alex Trebek, and in 2022 was officially tapped to host the show as one of Trebek's successors.
Ken lives in Seattle with his family and his dogs.