Seohyun was born on June 28, 1991, in Seoul, South Korea as an only child.
She attended Seoul Middle School and Daeyoung High School, from which she graduated on February 9, 2010 with the Achievement Award and currently attends Dongguk University like her fellow member, Yoona. Seohyun's major is acting.
She has been taking lessons on jazz piano. Seohyun was a trainee of SM Entertainment for six years and six months, which makes her the third longest SM-trained Girls' Generation member after Jessica (seven years and six months) and Yoona (seven years and two months), she was discovered in the 2003 SM Casting System.