Ryu Deok-hwan began acting on stage at the age of six. In 1996, he became part of the long-running MBC rural drama Lifetime in the Country. His career breakthrough came in 2006 when he played an amateur wrestler who wants to become a woman in the movie Like a Virgin. His performance in the film earned him numerous acting awards, including Best New Actor at the 27th Blue Dragon Film Awards and 44th Grand Bell Awards. In 2012, he was nominated for a Special Award at the SBS Drama Awards for his work in the fusion medical-fantasy drama Faith. That same year, he made his directorial debut in the short film Waiting for Jang Joon-hwan starring Oh Jung-se and Park Shin-hye. In 2020, he starred in the SBS series Nobody Knows, which scored him a Top Excellence Award nomination at the SBS Drama Awards.

Ryu Deok-hwan entered the military for his mandatory service in March 2016 and was discharged in December 2017. He married his long-time girlfriend in April 2021. His mother is a musical producer.