With all precincts reporting, Weatherford received a total of 9,523 votes, or 62 percent, while Byrne received 5,960 votes, or 38 percent.
In total, 15,483 voters cast their ballots in the race.
Janine Eveler, director of the Cobb Board of Elections, said there are 102,730 active voters registered in District 1.
Weatherford will now face Democrat Derrick Crump in November’s general election, although pundits predict the race has been decided due to the Republican stronghold in northwest Cobb.
Byrne and Weatherford have jousted for the District 1 seat occupied by retiring Commissioner Helen Goreham, since edging out three other candidates in the May 20 primary.