A 38-year-old man has been charged with arson after he allegedly set alight a unit in an apartment complex in Amaroo overnight.

At about 1.30am, ACT Fire and Rescue responded to reports of a structure fire on Emerald Way.

Upon arrival they found a second storey unit well alight, and quickly entered the building to contain its spread.

The fire was quickly extinguished a short time later with extensive damage occurring to the unit.

Several people were assessed by ACT Ambulance Service paramedics but did not require transport to hospital.

ACT Policing arrested a 38-year-old Amaroo man a short distance away from the fire and have charged him with arson, he faced the ACT Magistrates Court this morning.

Most residents were allowed to return to the building after standing in the cold for two hours.