CCTV footage shows the terrifying moment the buggy veers to the right and rolls over the edge of the platform, after the mum lets go of the handles to retrieve a dropped shoe.
The mother follows the buggy onto the tracks and two other passengers jump down from the opposite platform to help rescue the two-year-old boy.
The mother is then seen cradling the boy as the other passengers scramble to lift her belongings off the track and a train travelling in the opposite direction arrives at the station.
Story continues below the video
David Phillips was one of the bystanders who was about to board a train at Camberwell station in Melbourne, Australia, on Saturday (September 13), when he saw the buggy go over the edge.
"Without hesitation I just jumped into the pit to try to help out, do the best I could," he told 9NEWS.
"She was distressed. The kid was crying. Quite a few other people were concerned."
The boy, who has not been named, was taken to hospital after suffering 'minor facial injuries' in the fall.
More on Parentdish: Child in a buggy is blown onto tube track - seconds before train arrives
Suggested For You
SUBSCRIBE AND FOLLOW
Get top stories and blog posts emailed to me each day. Newsletters may offer personalized content or advertisements.Learn more