Firefighters say an ember from burning yard clippings, landed on the barn.
Fire crews received the call, just after 4 p.m. on Greenwood near North Avenue, just south of Sanger.
The barn is about a mile away from a residential neighborhood and the fire was threatening nearby structures.
Crews say they were forced to break down some nearby backyard fences to reach fire hydrants and get more water on the burning barn.
"We ran out of water fairly quick for the amount of fire that was involved," said Cal Fire public information officer Jeremiah Wittwer. "Having that water supply close was able to aid us in getting this knockdown fairly fast."
A plume of black smoke could be seen from various parts of Fresno County. ABC30 insider Rory Beasley shared drone footage of the fire as it burned this afternoon.
Several vehicles inside the barn were destroyed. No injuries were reported.
Fire crews are urging residents to maintain their yards and create defensible space in the morning before conditions become too dry during the heat of the day.
They also recommend mowing only green grass and to use weed eaters on dry grass to avoid accidentally sparking fires.