The emergency services were alerted to the blaze at the home on Parnie Street in the city centre on Friday evening.
The building was evacuated and no-one was injured.
Police have now launched an inquiry.
A Police Scotland spokesperson said: “Emergency services received report of a fire within a property on Parnie Street in Glasgow around 9.25pm on Friday, 30 July, 2021.
“The fire was extinguished by the Scottish Fire and Rescue Service and no-one was injured.
“Residents from the building have been evacuated and the road remains closed until the building is safe.
“The fire is being treated as wilful and enquiries are ongoing.”