A 50-year-old was taken to Victoria Hospital in Kirkcaldy after a fire broke out in a chalet in Kelty at 10:50 on Monday.
She has now been transferred to St John's Hospital in Livingston.
The Scottish Fire and Rescue Service said the cause of the blaze was still under investigation.
A Police Scotland spokeswoman said: "Police Scotland and the Scottish fire and Rescue Service responded last night following a fire at a travellers site in Kelty.
"A 50-year-old woman was seriously injured.
"A joint investigation is currently underway to establish the full circumstances of the incident."
A woman is in a serious condition in hospital with arm and chest burns following a fire at a travellers site in Fife.