Chuck Garcia, the president of Oakland Firefighters Local 55, said the vote was 242 to 104 in favor of making the concessions, which will help the city close its estimated $58 million shortfall.
He said firefighters will take an 8.85 percent pay cut for each of the next three years and give up two vacation days annually.
In addition, newly hired firefighters will have to work until age 55 to get their full retirement benefits, instead of the current age of 50.
Firefighters will continue to contribute 13 percent of their retirement costs in return for a provision that they won't be laid off, Garcia said.
Garcia said he had been nervous about whether his union's members would approve the concessions because "they are not happy about what they are giving up."
But he said, "Our members understand the city is in serious financial difficulty and had to help out."
The agreement extends the firefighters current agreement, which was to expire next year, until 2014.
Firefighters agreed to reopen their contract so it could be modified, Garcia said.
Most other major Oakland employee unions, including the union that represents police officers, have agreed to similar concessions to try to help the city balance its budget.
However, one major union, Service Employees Union Local 1021, which represents about 1,400 maintenance and park workers, hasn't yet announced its results.