The election was held Friday. The vote was 21 to 16 in favor of union representation.
The employees selected the International Association of Firefighters, local 4413, as their collective bargaining agent.
Wages, hours and working conditions will now be subject to negotiations between the county and the union.
All employees of Fire and Rescue in Walton County are now represented by the union, including the 16 who voted against and two employees who did not vote.
County Administrator Ronnie Bell says the county will fully comply with the law and its obligation to recognize the employees union.