York Regional Police said they were called to an industrial building at 25 Mural Street, belonging to Van-Rob Inc., around 4:20 p.m.
Two subcontractors were doing electrical work at the building and were standing on a scissor lift at the time of the incident, police said.
It's unclear exactly what went wrong, but one of the men was electrocuted and lost vital signs.
York paramedics transported the man to hospital, but he was pronounced dead there.
The 39-year-old man has not been identified at this time.
The Ministry of Labour is set to investigate the incident.