A homeless Harlem hospital patient was busted in the beating of an elderly man — after a cop recognized the suspect in a surveillance image and detectives tracked him down, police sources told The Post on Monday.

It wasn’t clear what the vagrant was being hospitalized for when he was nabbed in Sunday’s violent attempted robbery at a Midtown bodega, sources said.

But a cop knew the 34-year-old suspect from an unrelated case and recognized him in one of the surveillance images the NYPD released of the bodega incident, according to sources.

That officer gave the suspect’s name, Dominique Stanton, to detectives investigating Sunday’s caught-on-camera attack that left the 73-year-old victim hospitalized, and the officers tracked down the alleged assaulter, sources said.

Stanton was charged with attempted robbery, attempted grand larceny and assault, sources said.

The suspect is accused of initially trying to grab the elderly victim’s wallet while he was buying lottery tickets at a convenience store on Eighth Avenue near 40th Street around 10:50 a.m. Sunday, police said.

When the elderly man left the store, the suspect was captured on video tailing him before shoving the victim to the sidewalk and repeatedly kicking him while he was down.

At least three horrified bystanders could be seen on video backing away as the vicious assault unfolded.

The suspect eventually relented and fled empty-handed into the subway station on the same corner, police said.

Meanwhile, the victim was taken by EMS to Bellevue Hospital to be treated for swelling and an abrasion to his left eye.

Details of the arrest came as the NYPD said they were trying to track down another suspect wanted over an unrelated, unprovoked attack on a 68-year-old man earlier this month.

The second attack, which unfolded just blocks away from Sunday’s attempted robbery, resulted in the victim losing a tooth after he was punched in the face by the suspect, cops said.

The victim also suffered a head injury after falling to the ground and was taken by EMS to Bellevue Hospital, according to police.

The suspect, who was last seen wearing a checkered shirt over a blue hooded sweatshirt, fled into Penn Station.