The man walked into the store at 12 E. 57th St. about 2:50 p.m., police said, and asked to look at a Cartier Ballon Bleu wristwatch, police said. After being shown the watch and trying it on, the suspect then fled the store, heading east on East 56th Street toward Park Avenue.
No one was reported injured in the theft. Police declined to release the value or model of the watch, and a manager at Tourneau referred questions to the company's corporate headquarters.
Calls to the company's headquarters were not immediately returned.
Prices on the Tourneau website range from $4,350 for a stainless steel "small model" Ballon Bleu, to $45,400 for a "medium model" made of pink gold and diamonds.
Cops released surveillance photos of the alleged suspect, who was last seen wearing jeans and a striped, V-neck button-up sweater.
Anyone with information about the theft is asked to call the NYPD's Crime Stoppers hotline at 800-577-TIPS. Members of the public 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.