Scotrail said the minor derailment within its Ayr depot on Thursday night had led to a limited number of trains being able to travel to Glasgow.
Services between Ayr and Ardrossan Harbour to Glasgow Central have been hit, with buses replacing trains between Ayr, Girvan, Stranraer and Kilmarnock.
Engineers are working to get the train back on the rails.
Scotrail said: “We are sorry but due to a train having been involved in a minor derailment within a depot late last night, we have a limited number of available trains this morning at Ayr as they are unable to depart the depot just now.
“Our staff are continuing to work hard to get the affected train back on the rails so that we can get other trains out of the depot.”