Jang Dong-joo debuted as an actor in 2017 with minor roles in KBS2’s School 2017 and in tvN’s Criminal Minds. In 2018, he played a supporting character in the SBS series My Strange Hero. In 2019, he became part of the OCN drama Class of Lies. That same year, he appeared in the two-episode MBN series Loss Time Life. In 2020, he bagged a starring role in the comedy film Honest Candidate, which was a remake of the 2014 Brazilian movie O Candidato Honesto. In 2021, he was cast as one of the members of the fictional band LUNA in the SBS musical drama Let Me Be Your Knight.

Jang Dong-joo attended Sejong University.