The boy is believed to have been driving along Girraween Road in Graman, about 40 kilometres north-west of Inverell, with an 11-year-old passenger when the vehicle left the road.
Emergency services rushed to the scene and attempted to treat the 11-year-old driver but he died at the scene.
The passenger was flown to Lismore Base Hospital in a serious condition.
“Police established a crime scene and commenced an investigation into the cause of the crash,” NSW Police said in a statement.
Police have seized the ute for forensic examination.
A report will be prepared for the coroner.