Fire crews and the Coastguard were called to the harbour around 7.45am on Sunday after reports a motorboat was on fire in the marina.
When crews arrived half the boat was on fire in the cabin, with firefighters using waterjets to put the blaze out.
A spokesman for Lancashire Fire and Rescue said: “In total six firefighters wearing breathing apparatus brought the fire under control using jets and a hose reel jet.
“Firefighters extinguished the fire and made the scene safe.
“Firefighters used thermal imaging cameras to check that the fire was properly extinguished. The boat was severely damaged by the fire and a fire investigation will now be carried out.”
Fleetwood’s Coastguard team confirmed fears had been raised about the amount of fuel on board the vessel, but praised the actions of fire crews.
A spokesman added: “It was understood that there was approximately 700 litres of fuel along with a gas tank which also was a possible issue in respect of pollution.
“Fleetwood Coastguard prepared to launch a pollution prevention boom around the boat to prevent any contamination, however, following discussion with the port staff and fire crews boat was towed into the dry dock.”
No one was injured in the incident.