The video shows the officer fending off several men who appear to be ganging up on him inside the East Broadway subway station in the Lower East Side.
Police said the officer had asked the men, who are homeless and appeared intoxicated, to leave the station Sunday night after a woman said they were harassing her.
The men refused and then became combative, according to police.
The video shows one man charging at the officer and then falling off the platform and onto the tracks.
At that point, the officer asked that power to the tracks to be turned off while also calling for additional units to respond.
All five men were taken into custody but later released without charges.
Patrolmen's Benevolent Association's president Patrick Lynch said the men should be held accountable.
"As the District Attorney continues to decriminalize criminal behavior in the subways, we can expect to see the safety of our mass transit system deteriorate," Lynch said in a statement.
Meanwhile, Officer Syed Ali was honored for his actions inside the subway station.
New York City Councilman Chaim Deutsch met with the officers and honored him for his restraint and discipline.
I visited @NYPDTransit Task Force in North Brooklyn to thank Officer Syed Ali for his quick action to defend civilians and himself against five individuals attacking on a subway platform. Officer Ali showed restraint & discipline in how he de-escalated the situation. pic.twitter.com/xLe996P5ti— Councilman Deutsch (@ChaimDeutsch) December 25, 2018