Lightning is believed to have struck a unit on Mountain Chase Drive about 4 p.m., Cartersville Fire Department personnel said. The blaze was contained to the attic area of three units.
Three stations responded to the blaze, and crews ascended to the roof where vents were removed to allow smoke to escape the confines of the attic.
Residents of the complex off Tennessee Street were evacuated, and CFD crews remained on scene into the night.
CFD said the American Red Cross was called in to assist seven residents affected by the blaze.
There were no reports of injuries.