The man died at the scene in Kidderminster, and his death is not being treated as suspicious by police.
A spokeswoman for West Mercia Police said: "Shortly after 11am on Friday 6 May we were called to an address in Tower Close, Kidderminster where it was reported that a man had been seriously injured whilst using a chainsaw.
"The man, who was 79, died at the scene. Police are not treating the death as suspicious and a report has been prepared for the coroner."
A spokesperson for West Midlands Ambulance Service said: “We were called at 11.01am to reports of an injured patient at a private address off Comberton Avenue.
"We sent two ambulances, a paramedic officer, a MERIT trauma doctor and critical care paramedic and the Midlands Air Ambulance from Strensham.
"On arrival, crews found one patient, a man in a critical condition. Sadly, despite the best efforts, it quickly became clear nothing could be done to save the man and he was confirmed deceased on scene.”