Lee Dong-hwi made his big screen debut in the 2013 film South Bound. The following year, he landed his first television role in the KBS2 sageuk Joseon Gunman. In 2015, he appeared in the film The Beauty Inside, which earned him a Best Supporting Actor nomination at the 11th Max Movie Awards. His career breakthrough came later in 2015 when he played one of the main characters in the hit tvN series Answer Me 1988, which scored him Best New Actor nominations at the 52nd Baeksang Arts Awards and the 9th Korea Drama Awards. In 2017, he took home the Popular Star Award at the 6th Korea Top Star Awards for the comedy-drama film The Bros. In 2019, he starred in the mega blockbuster movie Extreme Job along with Ryu Seung-ryong, Honey Lee, Jin Seon-gyu, and Gong Myung. In 2020, he led the film Somewhere in Between, which gave him a Best Actor nomination at the 8th Wildflower Film Awards.

Lee Dong-hwi studied at the Seoul Institute of the Arts. He has been dating model and Squid Game star Jung Ho-yeon since 2015.