His election extends a decades-long line of African-American mayors in the mostly black city. The hard-fought victory started with a general election, then a runoff and a recount on Wednesday.
The results of the recount showed Reed with 714 more votes than City Councilwoman Mary Norwood. Norwood picked up just one vote in the recount. Because of the change, Fulton County elections officials said they would have to recertify the race on Thursday.
Norwood ran a strong grassroots campaign but fell short of becoming the city's first white mayor since 1973.
The 40-year-old Reed, who entered the race a few months ago as a virtual unknown, ended the contest strongly, passing Norwood in fundraising.