The blaze at Troon Station is thought to be centred on the ticket office and a nearby hairdressing salon on Barassie Street.
Photos from the scene show flames on the roof of the building with thick black smoke billowing into the sky.
Three Scottish Fire and Rescue Service (SFRS) engines have arrived at the station, with crews using an extendable ladder to put out the fire.
Details of any injuries are not yet known.
Services have been suspended at Troon station, with ScotRail warning customers that trains may be cancelled, delayed or revised.
Bus replacement services are currently being organised at Kilwinning, Largs and Ayr stations.
The SFRS have been contacted for comment.
Updates to follow.