Emergency services received calls after two men were hit by a car while walking along the footpath on Lane Street in Broken Hill at about 8.45pm on March 30.
A 19-year-old man and a 49-year-old man were treated at the scene before they were taken to Broken Hill Hospital in a serious but stable condition.
The older man was later transferred to Royal Adelaide Hospital, where he remains with serious head injuries.
Following an investigation into the circumstances, the 18-year-old allegedly behind the wheel was arrested at Broken Hill Police Station.
However, he was released pending further investigations.
Following extensive inquiries, police attended a home on Wyman Street, Broken Hill, and again arrested the 18-year-old man at about 9.15am yesterday.
He was taken to Broken Hill Police Station and charged with two counts of cause grievous bodily harm with intent to murder.