The crooks were forced to make their daring escape after a quick-acting member of staff trapped them inside the carriage half-way down the 201ft (61m) track.
Dramatic footage shows the thieves walking into the Bridgnorth Cliff Railway in Shropshire at 8pm on Sunday.
While the female cashier was distracted, one of the gang swiped a blue cash box from the ticket office of the 123-year-old railway.
When she realised what had happened she trapped the man’s two accomplices inside the carriage by stopping it halfway down the cliff and dialled 999.
But no officers arrived and the two men climbed out of the carriage door and hauled themselves up the steep track before running away on foot.
Director of the railway, businessman Dr Malvern Tipping, 55, released CCTV footage of the gang in a bid to track them down.