There was one slippery customer on board a train south of Sydney overnight. 

Passengers on the 6.54pm service from Kiama to Central on Tuesday were stunned to find they were sharing their carriage with a small snake that was slithering along the overhead luggage rack.

A NSW TrainLink spokesman said passengers on the South Coast Line service alerted staff as the train approached Wollongong station.

All passengers were moved off the carriage, which was locked for the rest of the journey to Sydney.

"Arrangements were made for a snake handler to meet the train on arrival at Central Station," the spokesman said.

He said the train arrived at Central just after 9pm and the handler removed the snake.

The snake was identified as a non-venomous Children's python, a popular pet among reptile enthusiasts.

It was not clear how the snake came to be on the train.