Franklin Township police say he was taken to Cooper University Hospital, where he died from his injuries.
Police Chief Matthew DeCesari said the incident happened Monday afternoon while the juvenile was working on the farm with an adult male.
"There were horses on scene, and it looked like they were possibly digging holes, maybe for the horses as a pond or something like that," DeCesari said.
DeCesari said the boy was operating the tractor with the adult when "it wound up flipping over on top of him."
The adult suffered minor injuries.
Officers from Franklin and Elk Townships, along with firefighters, responded and worked together to lift the tractor.
"They saw the tractor had been flipped over onto the juvenile. They immediately tried to lift the tractor off and were able to do so. The juvenile was lying in the puddle of mud, and they immediately began to perform lifesaving measures on him," DeCesari said. "They started doing CPR, and they were able to get a slight heart rhythm back."
Police said despite their lifesaving efforts, the trauma was too severe and the teen did not survive.
The Gloucester County Prosecutor's Office and Franklin Township Police are conducting a joint investigation into the circumstances of the incident.
"There is a potential for criminal charges, but that will be determined after the investigation is concluded," DeCesari said.
New Jersey Department of Labor laws indicate that no one under the age of 16 is allowed to operate a tractor on a farm.
No charges have been filed.