Police were called to the former Glamis Hospital building in Montpellier St at 4pm on Saturday after neighbours reported two 14-year-olds loitering around the abandoned property allegedly set a tree on fire.
When the neighbours noticed the burning tree, they rushed out with a garden hose and extinguished it.
Police tracked the teenage boys down and took them back to the station.
Their parents were called to come meet them and the pair were referred to Youth Aid, Snr Sgt Bond said.
Glamis Hospital, which was put up for sale last week, has been abandoned since 2011 and has become a magnet for vandals, illegal dumping and rats.
The existing building had deteriorated severely since 2011, especially after two suspicious fires which gutted it in 2017 and 2018.
Other suspicious fires have been reported at the site over the years, including when furniture was set alight in November 2023.
