After graduating from high school in 1970, Christensen was accepted to Harvard University, Yale University, and Brigham Young University (BYU). He "decided to make the decision a matter of prayer" and felt a "clear impression" to attend BYU, which had awarded him a full scholarship. Christensen majored in economics, and was classmates in his first-year economics course with future U.S. presidential candidate Mitt Romney and future Harvard Business School dean Kim B. Clark. While at BYU, he took a two-year leave of absence from 1971 to 1973 to serve as a volunteer full-time missionary for the LDS Church. He was assigned to serve in South Korea and became a fluent speaker of Korean. Christensen returned to BYU after completing his missionary service, and in 1975 graduated with an Honors B.A. "summa cum laude" in economics.