Wellington County OPP responded to a workplace accident in Arthur, Wednesday.
It happened around 3:30 p.m. in the Schmidt Drive area.
A 24-year-old Woodstock man was taken to a trauma hospital with serious injuries.
Provincial police say the man was working on a piece of heavy machinery when he was struck in the head by a large steel bolt.
No road closures are in effect in the area for the investigation.
OPP say the Ministry of Labour has been notified, and an investigation is underway.