Yoon is an internist in private practice in Santa Clara. She grew up in Seoul, Korea, and received an M.D. from Ewha Women's University, School of Medicine. After graduation, she moved to the U.S. and trained in Internal Medicine at San Joaquin General Hospital in Stockton, CA. She is Board-certified by the American Board of Internal Medicine. Yoon and her husband, also an internist, have two teenage daughters. In her spare time, Yoon loves to travel, read books, and spend time with friends.