Hwanhee debuted as the other half of the South Korean R&B duo Fly to the Sky along with Brian Joo in 1999. Later that year, they released their debut studio album Day by Day, which earned them a Best New Group nomination at the 2nd Mnet Music Video Festival. The duo has so far released nine full albums since their debut, including 2007’s No Limitations, which became their first number one album. In 2011, Hwanhee dropped his self-titled solo studio debut album.

Hwanhee made his acting debut as one of the main cast members of the MBC series Over the Rainbow. In 2008, he joined the first season of the MBC reality-variety show We Got Married, in which he was paired with R&B singer Hwayobi. In 2012, he starred in the movie Star: Radiant Love.

Hwanhee served as a public service worker for his mandatory military service from 2011 to 2013. In March 2020, Hwanhee was involved in a drunk driving incident.