Park Seo-joon began his entertainment career with an appearance in the music video of Bang Yong-guk’s single I Remember in 2011. In 2013, he starred in the dramas I Summon You, Gold and A Warm Word. The latter gave him the New Star Award at the 2014 SBS Drama Awards. His career breakthrough came in 2015 when he appeared in the MBC series Kill Me, Heal Me, which won him an Excellence Award at the MBC Drama Awards. That same year, he reunited with his Kill Me, Heal Me co-star Hwang Jung-eum in the hit MBC romantic comedy She Was Pretty, which scored him another Excellence Award at the MBC Drama Awards. In 2017, he collected numerous accolades for the KBS2 drama Fight My Way. Also in 2017, he landed his first film leading role in Midnight Runners, in which he received several Best New Actor trophies, including one from the 54th Grand Bell Awards. In 2018, he headlined the tvN series What’s Wrong with Secretary Kim, opposite Park Min-young. He bagged a Top Excellence Award at the 6th APAN Star Awards for his work in the drama. In 2020, he took on the leading role in JTBC’s Itaewon Class, which was hailed Best Drama Series at the 25th Asian Television Awards.

Park Seo-joon enlisted for his mandatory military service in 2008 when he was 19 years old. He was discharged in 2010. He attended the Seoul Institute of the Arts. He is the oldest of three brothers.