Police are appealing for information about the incident at Main Street in the town on Tuesday.
A PSNI spokesperson said: "Shortly after 2:25pm, police on patrol in the Coalisland area noted a fire had started at an unused premises in the area.
"Northern Ireland Fire & Rescue Service attended and extinguished the fire. An elderly man was treated for smoke inhalation following the incident following police evacuation of an adjoining flat.
"A number of commercial premises were evacuated, as emergency services dealt with the incident.
"Enquiries are continuing to establish the circumstances surrounding the incident, but at this stage the fire is being treated as deliberate."
Police are appealing to anyone with any information in relation to the incident, or who may have dash-cam footage available should contact police on 101 quoting reference number 894 12/04/22.