The zoo officials were expecting the 15-year-old panda, named Lun Lun, to give birth to a single cub.
"We had no reason to expect twins, although we had not ruled them out," said Dwight Lawson, deputy director of Zoo Atlanta.
Zoo officials are working with animal care workers from the Chengdu Research Base of Giant Panda Breeding, where Lun Lun and her 15-year-old partner, Yang Yang, were born.
"This is a success we share with all of our fellow zoological organizations working to understand and protect this iconic species, and we share our joy with our local community and with our colleagues in China," said Raymond B. King, Zoo Atlanta's president and CEO.
"Twins are an entirely new scenario for Lun Lun, Zoo Atlanta and our animal care teams, who will no doubt be extremely busy over the next few months," his statement added.
Zoo spokeswoman Keisha Hines said less than 1,600 giant pandas are believed to be living in the wild.
Giant pandas typically only care for one cub when twins are born in the wild, which usually leads to only one of the twins surviving, she said.
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