It happened around 6:30 Saturday night on the 5600 block of Old Capitol Trail near Delaware Park Drive.
Fire crews reported heavy flames showing upon arrival.
The blaze was brought under control with the help of neighboring fire companies.
The building, which consisted of six apartments, suffered an estimated $25,000 in damages.
No injuries were reported but several residents are being assisted by the Red Cross.
Investigators are still trying to determine the cause.