Three passengers have been praised for crawling underneath a Sydney train to rescue a trapped child on Monday morning.

The young girl fell under the train at Wolli Creek Station in Sydney’s south about 9.15am.

As her mother became distressed, three men jumped off the platform and began looking for the girl under the carriages.

As other commuters tried to comfort her, the mother was told the toddler had been found near the front of the train.

“It’s OK, they’ve got her,” one passenger was heard saying in a video posted online.

The young man who found the girl was then filmed handing her over to her mother, reassuring her “she’s fine, she’s fine”.

A Sydney Trains employee then thanked the man and shook his hand.

The mother said it was the first time her daughter had been on a train and it “might be the last for a while”.

“She freaked out and tried to fling herself back off the train,” the mother was heard saying in the video.

Joseph Mourtada, 36, filmed the moment the mother and daughter were reunited, and said he was relieved there were no injuries.

Mr Mourtada was walking up the stairs to the platform when he saw the commotion and the distressed mother “shaking”.

“She was screaming that her girl was under the train,” he said.

“I hear all of this noise and people asking the guards to stop. It was already stopped.

“Everything happened very quickly.”