Fire crews were called to the farm on the Center Road just after 11:00 p.m.
When they arrived they found a building and part of the barn leveled and engulfed in flames.
Firefighters on scene said the building used to be the farm's milking parlor, but had been converted into a tool shed.
Garland Fire Chief Henry Burrill said "We got here, and the building was fully involved, so my first thought was, 'save the dairy barn.' This was where they had the furnace, the boiler room, so I'm guessing it was something in that area."
Crews from five towns were able to contain the fire ....
No people or animals were hurt.