He was taken to Vanderbilt University Medical Center, where he was pronounced dead, authorities said.
Officials weren't able to say whether the child was out trick-or-treating when it happened.
Emergency medical technicians from the Nashville Fire Department and officers from the Metro Nashville Police Department responded to the scene.
The Nashville Electric Service reported on their outage map online that crews had been dispatched to the area where the child was struck to take care of the downed line.
Severe weather and strong winds knocked down trees and power lines throughout Middle Tennessee as a cold front pushed into the area.