Taieri Gorge Railway chief executive Murray Bond said graffiti was applied to carriages parked at a siding near Cumberland St and at workshops in Hillside Rd early on Sunday in separate incidents.
As a result of the vandalism, a carriage was removed from a Taieri Gorge excursion on Sunday and passengers were seated in other carriages.
Carriages were vandalised between six and eight times a year, with each case typically costing the company up to $3000, Mr Bond said.
"We are really annoyed because, although police respond, it seems the penalties for vandalism are a complete laugh. Tagging and vandalism can cost between $2000 and $3000," he said.
The carriages, when not in use, were stored over about 3km of railway yard.
Although staff were in the area up to 16 hours a day, seven days a week, the size of the rail yard made it impossible to prevent all vandalism.
On August 23, windows were broken on carriages in the company's yard in Cumberland St, where they were waiting to be refurbished.
A week earlier, graffiti was sprayed on the side of several carriages at a nearby railway siding.
Senior Sergeant Brian Benn, of Dunedin, said police were making inquiries about recent vandalism of rail carriages in Dunedin.
