He's struck at least five times in Greenwich Village and Gramercy Park.
The suspect approaches the victims, grabs the chains from around their necks, and then runs away.
No one was seriously injured in any of the incidents.
The suspect is described as a black man in his 20's, 5'7"-5'10", with a thin build, bald head, and wearing a blue baseball cap, and bright blue sneakers.
Anyone with information is asked to call Crime Stoppers at (800) 577-TIPS (8477).
You can also submit your tips by logging onto Crime Stoppers' website at www.nypdcrimestoppers.com or by texting your tips to CRIMES (274637), and then entering TIP577.