Kim Won-hae began his acting career on stage before making his big screen debut in the 1998 film Spring in My Hometown. Since then, he has become one of the most visible actors on screen in his home country. In 2011, he joined Season 1 of the late-night television sketch comedy show Saturday Night Live Korea and left after four seasons. In 2014, he became part of the smash hit epic action-war film The Admiral: Roaring Currents. That same year, he played one of the bandits in the period adventure film The Pirates. He also had roles in the movies The Himalayas and A Violent Prosecutor, which were released in 2015 and 2016, respectively. In 2017, he portrayed a criminal investigator in the SBS series While You Were Sleeping, which won him Best Supporting Actor at the SBS Drama Awards. He was also nominated for Best Supporting Actor at the 2017 KBS Drama Awards for his work in the sageuk Hwarang and in the workplace drama Chief Kim. In 2018, he took home the Best Supporting Actor trophy at the KBS Drama Awards for The Ghost Detective and Are You Human Too. In 2021, he earned a Best Supporting Actor nomination at the SBS Drama Awards for his performance in One the Woman.

Kim Won-hae majored in theater and film at the Seoul Institute of the Arts.