A crook wearing a long black wig robbed a Manhattan bank Saturday afternoon — and was busted with a little help from a cab driver, police and the cabbie told The Post.

John Sidney, 46 — also known as Madea Sidney — entered the Chase Bank on Sixth Avenue near West 4th Street at noon and passed a teller a note demanding cash, cops said. The teller handed over $500 and the thief bolted.

Sidney quickly hailed a yellow cab and asked for a ride to West 42nd Street and Eighth Avenue, said driver Thierno Diakhate — who thought Sidney was a woman. It was not clear if Sidney was in disguise or is transgender.

Once they hit 14th Street, Sidney announced a change of plans and asked to be taken to Brooklyn.

“I took Flatbush Avenue … and made a left onto Fulton, went all the way down to Gates Avenue, where I got a call from an officer,” said Diakhate, 33. “My phone was ringing, but I could not pick it up because I was driving.”

But once he reached his be-wigged passenger’s destination on Gates Avenue near Marcus Garvey Boulevard in Bedford-Stuyvesant, he finally glanced at his phone.

“I realized I got five missed calls,” Diakhate said. “I saw I got a message from an officer of a picture of the lady. In the message, the officer said, ‘We sent you this picture because we believe this lady got into your cab.’ The officer said the lady robbed a bank in Manhattan. I texted the officer back, ‘She’s still in my cab.’ ”

Cops apparently got Diakhate’s cell number from the cab company.

Sidney soon asked to leave the cab, only to wait outside for a few minutes and get back inside with a man who asked to be dropped off about three blocks away. Sidney handed him something before he got out of the car, the cabby said.

Sidney exited minutes later, at Throop Avenue and Van Buren Street, Diakhate said.

“I was waiting for which building she was going to enter, where she was going to go,” he added.

As instructed, he drove to the nearest traffic light to meet police.

“When [the cops] got into the cab, when we were heading up to where I dropped her off . . . we saw her try to get into another cab,” Diakhate said.

Sidney was instead busted and charged with robbery, police said.

Diakhate, a cabby for three years and is taking accounting classes, had one complaint: Sidney was cheap on the tip. “The fare was $41.42,” he groused. “She gave me $50 and asked for $5 back.”