When fire fighters returned to their station in Nelson, Lancashire, they found items, including their wallets and watches, had been stolen.
The burglars broke into the station between 12.30am and 5am on Friday.
They forced their way through internal doors and ransacked almost every room in the station.
Two fire engines from the station had been dispatched to a nearby home where the second floor of the terraced property was on fire.
Working with crews from Colne and Hyndburn, the crew had to use breathing apparatus, hose reels, triple extension ladders and a thermal imaging camera in a bid to extinguish the fire.
Sergeant Kathryn Mather of Lancashire Police said: “This is a disgraceful crime against our emergency services colleagues who were out doing their job and protecting the public.
“We’re committed to finding those responsible and are appealing to anyone with information to get in touch.
“If you saw anybody acting suspiciously in the area, please let us know.”
Lancashire Fire Service’s Twitter account posted a message, saying: “Let’s try and catch these ‘people’ and help our firefighters get their belongings back.”
Anyone with information should police by emailing email@example.com, or calling 101 quoting log number 173 of June 22.