The alleged attack happened Thursday and the girl's mother reported it to authorities Sunday, Acworth police Capt. Wayne Dennard said.
"The juvenile victim stated that an 8-year-old boy and two 9-year-old boys that she had been playing with earlier pulled her into a wooded area, where one of the boys raped her," Dennard said.
Calls to the Acworth Police Department and Cobb County prosecutors seeking further detail were not returned Monday morning.
Acworth is 28 miles (45 kilometers) north of Atlanta in the city's fast-growing outer suburbs.