Jang So-yeon got her first taste of acting in 1999 when she was cast in a student film titled Tear Puddle. She then landed an uncredited appearance in the 2001 coming-of-age film Take Care of My Cat, which was followed by a role in the movie Desire in 2002. In 2007, she joined the cast of the MBC medical drama White Tower. She then became part of MBC’s hit sageuk Dong Yi in 2010. In 2015, she acted alongside Moon Geun-young and Yook Sung-jae in SBS’s Village: Secret of Achiara, which gave her a Special Award nomination at the SBS Drama Awards. That same year, she appeared in the films Gangnam Blues and Veteran. In 2016, she played Kwak Do-won’s wife in director Na Hong-jin’s award-winning horror film The Wailing. In 2018, she starred with Sohn Ye-jin and Jung Hae-in in JTBC’s Pretty Noona Who Buys Me Food, which won her Best Supporting Actress at the 6th APAN Star Awards. In 2019, she was nominated for an Excellence Award at the MBC Drama Awards for Welcome 2 Life. Later in 2019, she bagged a supporting role in the top-rating tvN series Crash Landing on You.

Jang So-yeon majored in English and Chinese language at Sookmyung Women’s University. She dated her The Wailing co-star Kwak Do-won.