The 60-year-old actor was a passenger in a vehicle which collided with another car in West Hollywood on Friday.
Paramedics were called to the scene and the "Bad Santa" star was taken to the local Cedars-Sinai Medical Center to receive treatment for a head injury, according to TMZ.
However, a representative for Thornton has downplayed the accident, telling the outlet the actor was only hospitalised as a precaution.
He was subsequently given the all clear and discharged.
Thornton refused to let the incident disrupt his schedule and later returned to work on the set of his latest project.