Firefighters were called to a suspected fire in the engine room of HMS Tyne, moored at Falmouth Docks, last night.
Crews from Falmouth, Helston and Redruth raced to the scene after a call to the emergency services at 8pm.
However, the fire was already out when they entered the smoke-logged engine room of the fishing protection vessel.
Falmouth Fire station watch manager Martin Mellor, who attended the incident, said: “We had to restart and ventilate the compartment in the engine room."
Three sets of breathing apparatus were used during the incident, with four crews and one operational support vehicle in attendance.
The ship’s ventilation system was used to clear the smoke and the firefighters had left the scene by 9.30pm.
The Royal Navy ship weighs 2000 tonnes, and is 80 metres in length.