In the first and third robberies, tellers handed over cash to the robber, the police said, but he left empty-handed in the second encounter.
The police do not believe that the man displayed a weapon, though they were still gathering information late Friday afternoon.
The mini-crime wave began at around 2:15 p.m., when the robber entered a branch of the Apple Bank at 1321 Kings Highway. He handed a teller a note, was given some money and left, the police said.
About 15 minutes later, the man walked into a Capital One branch at 1226 Kings Highway, the police said, and handed over a note, but did not get any cash.
About 2:40 p.m., the suspect entered an HSBC bank branch at 1621 Kings Highway. Again, a note was handed over and he obtained some money, the police said.
The police did not immediately say how much money the man had taken.
The robber’s spree shows “a certain amount of perseverance,” said Thomas W. McKenna, a retired first-grade detective with the New York police.
“It’s very unusual for a guy to do three banks in a row, that close together, and to stay in the same area.”
Mr. McKenna added: “He’s looking for a score, there’s no doubt about that. And he’s nonsectarian about which bank he goes to.
“Any bank is open play for him.”
The robber was described as Hispanic, about 5-foot-7, and 150 pounds. He wore black pants, a red shirt and a red baseball hat.
Bill Giannopoulos, owner of Madison Florist and Decorators, across Kings Highway from the Apple Bank branch, said he did not realize anything was happening until the street was swarming with police officers and a helicopter was circling overhead.
“It’s scary,” he said. “I don’t know what’s happening in the neighborhood.”