Lee Seung-joon began his acting career on stage before making his screen debut in the 2001 short film Falling Season. In 2009, he appeared in the thriller film Handphone and then in the drama film Heartbeat in 2010. In 2011, he became part of the hit period action movie War of the Arrows. In 2012, he was cast in the LGBT-themed film Two Weddings and a Funeral. In 2014, he acted alongside Choi Min-shik in the blockbuster war epic The Admiral: Roaring Currents. That same year, he joined the high-rating tvN workplace drama Misaeng. In 2016, he worked with Song Joong-ki and Song Hye-gyo in the widely popular KBS2 series Descended From the Sun. In 2018, he played Emperor Gojong in tvN’s Mr. Sunshine. In 2021, he bagged a role in the Korean-French film Vanishing: Unsolved Case.

Lee Seung-joon attended the Seoul Institute of the Arts’ theater department.