Tiffany & Co., betting that diamonds also may be a boy’s best friend, will open its first boutique devoted exclusively to men’s jewelry and accessories in September.

“Tiffany & Co. The Men’s Store” will open in an Isetan department store in Tokyo, the company said yesterday in a statement.

Tiffany, based in New York, said it will introduce merchandise specifically designed for men at this location, including diamonds set in gold as well as platinum; designs from Paloma Picasso, Elsa Peretti, Jean Schlumberger, and Frank Gehry; and watches and accessories.

“It is a relatively small category but we think it has growth potential,” Tiffany spokesman Mark Aaron said in an interview. He declined to say how many such boutiques Tiffany envisions and wouldn’t provide men’s jewelry sales figures.

The shares fell 39 cents to $51.69 at 4:01 p.m. yesterday in New York Stock Exchange composite trading and have gained 32% this year. The company operated 171 stores and boutiques worldwide at the end of the first quarter.

The men’s boutique will be on the first floor of the renovated men’s building of the department store, Tiffany said. Tiffany will join other brands that are being incorporated into the refurbished space, Mr. Aaron said.

Tiffany, founded in 1837 in New York, is the world’s second-largest luxury jewelry retailer and trails Cie Financiere Richemont AG, the maker of Cartier watches, in sales.