Hoverlab, a South Korean news commentary site on YouTube, claimed that the actor and the late actress Kim Sae-ron had been in a six-year relationship since she was 15 years old.

According to the actor's agency's statement, Kim Sae-ron was 19 at the start of the relationship and Kim Soo-hyun was 31.

After confirming that they were in a relationship, Kim Soo-hyun refuted the allegations that he dismissed Kim Sae-ron’s call for help over a debt connected to a drunk driving incident (DUI) that the late actress was involved in.