Song Seung-heon got his start in the entertainment industry as a model for a jeans brand before transitioning into acting through the 1996 MBC sitcom Three Guys and Three Girls. He made his big screen debut in the 1999 film Calla, which scored him a Best New Actor nomination at the 20th Blue Dragon Film Awards. In 2000, he starred in the hit KBS2 series Autumn Fairy Tale, which launched him into Hallyu stardom. In 2008, he led the MBC drama East of Eden, which won him the Daesang at the MBC Drama Awards. His work in the series also earned him a Best Actor nomination at the 45th Baeksang Arts Awards. In 2011, he was paired with Kim Tae-hee in the MBC romantic comedy My Princess and then played the titular character in the MBC fusion sageuk Dr. Jin in 2012. In 2013, he portrayed a cold-hearted loan shark in When a Man Loves, which also aired on MBC. In 2014, he took home the Popular Star Award at the 35th Blue Dragon Film Awards for the erotic romance film Obsessed. In 2017, he joined Lee Young-ae in the SBS fantasy sageuk Saimdang, Light’s Diary, which gave him a Top Excellence Award nomination at the SBS Drama Awards. In 2021, he took on the male lead role in the tvN crime procedural series Voice 4.

In late 2004, Song Seung-heon got involved in a draft-dodging scandal after it was revealed that he previously faked his urine samples to evade conscription. Amid public backlash, he immediately enlisted for his mandatory military service. He was discharged in November 2006. He dated Chinese actress Liu Yifei, whom he co-starred with in the film The Third Way of Love.