Jay Mortenson swam at Stanford University in college, helping them extend their long-running streak of Pac-10 Championships. He won individual NCAA titles in the 100 fly and 100 back in 1988, and defended his 100 fly title in 1989. Primarily a backstroker, Mortenson led off the Stanford medley relay team that won the NCAA title in 1987. He also led off Stanford’s medley relay to win three consecutive Pac-10 titles from 1987-89. Internationally Mortenson won a gold in the medley relay at the 1987 Universiade, where he won bronze in the 100 backstroke, in addition to his 1988 Seoul Olympics gold medal in the medley relay.
Mortenson later became an investment banker in the Los Angeles area. He was inducted into the Stanford Athletics Hall of Fame.