The town's first station opened in 1889, but when the line was duplicated and new tunnels were built between Waterfall and Otford, it was moved to its present location on May 30, 1915.

To mark the occasion, morning commuters were entertained by the NSW Railway Brass band - who had made an early-morning trip from Sydney to the station.

Before they boarded their train, commuters could also enjoy some scones and cream and, of course, a birthday cake.

NSW TrainLink CEO Rob Mason took part in the morning's festivities. He said there were other stations in the network that had passed their 100th birthday but there was "something special" about Helensburgh.

"This is quite a unique one," Mr Mason said. "It's an island platform and it's very curved. Some of the photographs taken when it was being built show the very big cutting behind it. It was quite an engineering feat to build it at that time."

He said the embankment behind the station still created challenges today when it came to delivering infrastructure like car parks.

Heathcote MP Lee Evans was on hand to unveil a plaque in the former signal box that now serves as a waiting room. He said it was impressive to think the station was built 100 years ago.

"When you consider back in 1915 when they moved the railway station from up the road to down the bottom of the valley it was a pretty big task," Mr Evans said.

"It would cost millions of dollars now if we were to do it."

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