In each case, he handed the tellers a note and never displayed a weapon, police said.
The first robbery happened on July 25 about 2:25 p.m. at a Capitol One Bank at 2083 Hylan Boulevard on Staten Island, police said. The suspect made off with an unspecified amount of cash.
He then struck two days later on July 27 about 12:05 p.m. at a Northfield Bank at 283 Kings Highway in Brooklyn, again fleeing with an unspecified amount of money, police said.
Finally, two days after that on July 29 about 10 a.m., he hit a Citibank at 1871 Nostrand Ave. in Brooklyn, where he left without getting any money.
Police described the suspect as a 50-to-55-year-old man, about 6 feet tall. He was last seen wearing a black waist-length jacket, black pants and a black baseball cap.
Anyone with information is asked to call Crime Stoppers at (800) 577-TIPS (8477). You can also submit tips by logging onto the Crime Stoppers' website at www.nypdcrimestoppers.com or by texting tips to CRIMES (274637), then entering "TIP577."