Authorities say the child was separated from his father as the doors were closing on an uptown W train at 14th Street-Union Square.
Train Operator Christopher Lopez and Conductor Arron Corrian noticed the child at 28th Street.
They let passengers off their train and Corrian stayed with the child until police officers arrived.
Less than a half-hour later, the happy reunion between father and son occurred.
"Due to the keen observation and diligence of the crew, this story has a happy ending. Thank you to Christopher and Arron for your care and attention during a tense situation," the MTA said.
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