Hong Seo-young made her acting debut with a main role in the 2016 musical Dorian Gray, which earned her a Female Rookie Award nomination at the inaugural Korea Musical Awards. In 2017, she landed her first screen role in the tvN series The Liar and His Lover. She also contributed her voice to the drama’s official soundtrack. In 2018, she joined the OCN paranormal crime thriller Children of a Lesser God. In 2019, she appeared in tvN’s Her Private Life and SBS’s My Absolute Boyfriend. In 2022, she was cast in a supporting role in the second season of JTBC’s The Good Detective.

Hong Seo-young attended Chung-Ang University. She has an older brother named Hong Min-ki, who used to play volleyball for Hanyang University.