A professional logging crew were working along a stretch of forest on Lake Lenthall road, near Duckinwilla, when the incident occurred.
It is believed that the man, a Gympie local in his late 40s, was standing on a deactivated harvester to make repairs, when he slipped and fell between the gears of the machine.
He suffered serious compression injuries to both his legs as a result.
Multiple Queensland Ambulance Service crews attended the scene, before the CareFlight helicopter was tasked just before 7.20am.
The patient was flown in a serious but stable condition to Bundaberg Hospital.