The Scottish Fire and Rescue Service was alerted at 6.56pm on Saturday, 22 October to reports of a fire at the former Wellbrae Primary School building in Forfar.
Crews from Forfar, Dundee, Kirriemuir and Brechin were mobilised to the incident.
The fire was split into three separate sectors and crews immediately commenced external firefighting operations.
Six appliances were at the incident ground at the fire's height. An aerial rescue appliance was also used to douse flames that had broken through the building's roof from above.
No injuries were reported and the fire was eventually extinguished at 2am.
A further inspection of the building will take place this morning.