A prostitute allegedly stole an off-duty NYPD cop’s car — with his gun on the front seat — after he left her sitting in the vehicle while stopping at an ATM in Brooklyn early Tuesday morning, police sources told The Post.

Police arrested the hooker and recovered the car Wednesday — but the gun is still missing, sources said.

Officer Ali Sheppard was in his personal car, a 2015 Jeep Wrangler, when he hired Taquanna Lawton — known as “Unique” — at Liberty Avenue and Sackman Street in Brownsville around 12:15 a.m. Tuesday, sources said.

They were headed to a motel in East New York, but before the rendezvous, Sheppard, 38, made a quick stop to withdraw cash at an ATM at the Imperial Hotel.

That’s when Lawton, 20, allegedly jumped in the driver’s seat of the Jeep, which was still running, and drove off, with his Smith & Wesson pistol on the front seat.

Cops recovered the car and arrested Lawton in East New York just after midnight Wednesday, police said.

Sheppard, who’s been on the job for 13 years, has been suspended, police said. He raked in $105,819 last year, including overtime, according to SeeThruNY.

Officials are investigating whether he’ll be hit with any charges.

“He was immediately suspended and he’ll be facing some disciplinary action,” NYPD Commissioner James O’Neill said at an unrelated press conference Wednesday. “We’re working on the investigation.”

Additional reporting by Ben Feuerherd