The airport is the world’s busiest, handling more than 250,000 passengers and almost 2,500 flights every day.
Passengers were left in darkened terminals or on board planes.
Power is now restored at the airport, but over 1,000 flights were cancelled with hundreds more cancellations scheduled for Monday.
Many flights scheduled to arrive from other airports were being diverted elsewhere or held at their departure airport.
In a statement, the airport confirmed they had suffered a power cut shortly after 13:00 (18:00 GMT) on Sunday. Flights are expected to resume at 06:00 on Monday (11:00 GMT).
Georgia Power, which supplies the airport’s electricity, said it believed a fire at an underground electrical facility was to blame for the power cut. Officials said a piece of its switchgear could have failed and started the fire, causing cable damage.
Daawo sawiro: Garoonka diyaaradaha ugu mashquulka badan oo mashaqo qabsatay
Garoonka diyaaradaha caalamiga ah ee Hartsfield-Jackson oo ku yaalla magaalada Altanta ee dalka Maraykanka ayay korontadii ka tagtay taasoo sababtay in qayb ahaan la xiro, duulimaadyo badanna dib loo dhigo.
Garoonkan diyaaradaha ayaa ah midka ugu mashquulka badan adduunka oo dhan, waxaana maalinkasta adeegsada 250,000 oo rakaab ah iyo 2,500 oo duulimaad.
Dadkii safrayay ayuu mugdigu haleeyay iyaga oo qaarkood ay garoonka ku dhex jiraan kuwo kalana ay diyaaradaha saaran yihiin.
Diyaarado soo dagi lahaa ayaa garoomo kale loo weeciyay, kuwo kale oo ka duuli lahaana garoonka ayaa lagu sii hayay.
War qoraal ah oo uu garoonku soo saaray ayaa lagu sheegay in ay korontadu go’day Axaddii sagaalka ama saddexda fiidnimo Saacadda geeska Afrika.
Georgia Power oo ah shirkadda korontada siisa garoonka ayaa sheegtay in ay rumaysan yihiin inuu dhibkani ka dhashay dab ka kacay korontada dhulka hoosteeda marta ee garoonka.
Waxay sheegtay in aysan garanaynin waxa sababay dabka, balse ay rajaynayso in ay korontada soo celiyaan saqda dhexe ee Axadda wakhtiga deegaankaas.