Lee Hak-joo debuted as an actor in the 2012 short film Sweet Sorrow and has since appeared in numerous TV and movie productions. In 2015, he played Kim Seul-gi’s younger brother in tvN’s Oh My Ghostess. He also had supporting roles in the 2018 tvN series Memories of the Alhambra and the 2019 KBS2 drama Justice. His career breakthrough came in 2020 when he portrayed an abusive boyfriend to Shim Eun-woo’s character in the top-rating JTBC series A Couple’s World, which earned him an Excellence Award at the 28th Korea Culture and Entertainment Awards. Also in 2020, he acted alongside Jung Il-woo and Kang Ji-young in the JTBC romantic comedy Sweet Munchies. In 2021, he starred in the Netflix action drama My Name and the JTBC psychological thriller series Artificial City. That same year, he was nominated for Best New Actor at the 41st Blue Dragon Film Awards for his work in the movie Welcome to the Guesthouse.

Lee Hak-joo attended Hanyang University’s theater and film department.