The station, located at 595 Mini Drive, closed in July 2010, along with Station 26 on Fulton Avenue in Glen Cove, while the Vallejo was going through bankruptcy proceedings.
Fire personnel from those stations transferred to Station 27 in northeast Vallejo and Station 22 in south Vallejo.
Vallejo received a two-year Staffing for Adequate Fire and Emergency Response, or SAFER, grant from the Federal Emergency Management Agency on July 1 of last year. That allowed the city to hire 10 firefighters and purchase two new fire engines, Vallejo Fire Department engineer and spokesman Mark Libby said.
The 10 firefighters began training on Feb. 27, and Station 25 became fully staffed again on June 26, Libby said.
At one time, only four of Vallejo's eight fire stations were in operation, but now there are six open stations, Libby said.
He said that reopening Station 25 will improve response times to structure fires in north Vallejo and the rest of the city.
The two new fire engines will go to two of the city's busiest stations, 23 and 24, where the existing fire engines have high mileage, Libby said.
Each fire station is staffed by nine firefighters. The 10th firefighter hired with the grant money will fill in for injured firefighters or those on vacation.
At each station, three firefighters are on duty at any given time, and work 48-hour shifts, Libby said.
There are no plans yet to reopen the other two fire stations, Libby said.
The open house at Station 25 took place between 10 a.m. and noon.