An anonymous tip led police to the child at the station on W. 34th Street and 7th Avenue just before 9:30 a.m.
The baby girl, described as a newborn, was found wrapped in a blanket at the bottom of a staircase leading to the 1/2/3 train platform.
The baby was taken to a local hospital by police and was said to be conscious and alert.
Her condition was described as stable.
New York City Transit President Demetrius Crichlow called that "the miracle on 34th Street."
"I'm calling it the 'Miracle on 34th Street,' the FDNY and police department responded, they found a baby that was unattended," Crichlow said. "The baby was taken to the hospital and is in stable condition, we don't have any other additional information on top of that, but just grateful for the work of the NYPD for responding and caring for the baby."
Investigators are looking at video footage from the many cameras throughout the station to determine who left the baby and why.
A spokesperson with the Administration for Children's Services released a statement saying, "We are grateful to the first responders for ensuring this newborn's safety. The ACS team has been deployed to ensure the ongoing well-being of the baby."
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