Krystal was born in San Francisco, California, where her family from South Korea settled in the 1980s. During a family trip to South Korea in early 2000, when Krystal was five years old, she was spotted by talent agency SM Entertainment, which earned her a cameo appearance in Shinhwa's "Wedding March" music video. The agency saw potential in Krystal and offered her singing and dancing lessons, opting to professionally train her in a singing career. However, the offer was turned down by her parents, reasoning that Krystal was too young.
In 2002, Krystal began appearing in television commercials. She first appeared in a Lotte commercial with Korean actress Han Ga-in. In 2006, her parents allowed her to join SM Entertainment, and the agency enrolled her in dance classes, including hip hop and jazz