Zoe Ferguson, 14, was last seen in Inverkeithing at around 3.40pm on Friday April 26.
It is believed she boarded a train to Edinburgh Waverley from Inverkeithing and has not been seen since.
The youngster is described as slim with long brown hair with blonde tips and was last seen wearing a long green jacket, black leggings and a black skirt.
Concern is growing for Zoe as her disappearance is out of character.
Police have released a CCTV image of the teenager inside the train station.
Sergeant Lesley Duncan, of Dunfermline police station, said: "We believe Zoe has boarded a train from Inverkeithing to Edinburgh Waverley.
"Zoe has gone missing before but never for this length of time and we, as well as her family, are concerned."
Anyone with information of Zoe's whereabouts are asking to contact Police Scotland on 101 quoting incident number 2972 of 26 April 2019.