WALL STREET JOURNAL | RAY A. SMITH

On a recent weekday afternoon, Tommy Hilfiger was in his office clad in his signature warm-weather uniform: navy blazer, white shirt, crisp chinos and penny loafers, no socks. Only now, there was a crucial difference. Gone was the big, yacht-captain style, double-breasted blazer with brass buttons and baggy pleated khakis.

The change mirrors a shift at his company. His recent runway collections are sleeker and more urbane than in the past. He credits the "specialists" he has tapped to rejuvenate his women's and men's runway collections.

In one of the more unusual relationships in the fashion industry, Mr. Hilfiger has hired two critically acclaimed younger designers, Peter Som in 2009, and last year Simon Spurr, as creative consultants.

"It's my formula. It's my vision," Mr. Hilfiger says. "But I wanted someone to come in who respects the vision but would want to maybe modernize it a bit."

The hires are part of Mr. Hilfiger's broader effort to refresh his 26-year-old label's image in the U.S., particularly among luxury consumers.

High-end shoppers are taking notice. Over-the-knee, high-heeled lace-up women's duck boots Mr. Som dreamed up in collaboration with Mr. Hilfiger last year turned out to be one of the label's most buzzed-about and sought-after items in years. The label's retail prices have increased approximately 15% over the past two years. Net sales for the company's products rose 14.5% in 2010.

Critics are noticing, too. Tommy Hilfiger witnessed some of its most enthusiastic runway-show reviews in years since the two young designers came on board. Reviews noted the women's clothes "felt luxurious and sophisticated in a new way" and the men's line may have marked its best interpretation of preppy to date. Mr. Spurr, 36 years old, is one of three nominees for menswear designer of the year from the Council of Fashion Designers of America, whose awards ceremony takes place June 6.

With its popular colorful, preppy aesthetic, Tommy Hilfiger was one of the hottest American brands in the 1990s. At its peak, the company, acquired last year by apparel giant Phillips-Van Heusen Corp.,PVH -1.32% generated nearly $2 billion in annual sales in the U.S. But overexposure and changing tastes caused its popularity to wane considerably in the U.S. Its red, white and blue, logo-heavy look was seen as outdated. The label took a two-year hiatus from the New York fashion week runways in 2005 as it repositioned itself in the U.S. Meanwhile, the brand thrived in Europe, where it had a more upscale reputation and look.

Mr. Hilfiger says he is encouraging the designers to come up with modern interpretations of his signature staples. "I had an in-depth conversation with Peter on what New England preppy was all about," Mr. Hilfiger says.

The two men took a field trip in late 2009 to Mr. Hilfiger's home in Greenwich, Conn. They looked through Mr. Hilfiger's closet and that of his wife, Dee. "We were talking about how when Dee went to college she wore duck boots all the time," Mr. Som, 40, says. "I have my own duck boots, so I thought it would be fun to take iconic items and spin them, so I came up with making the boots sexier."

The result: High-heeled duck boots. "It was one of the most successful items we've had," Mr. Hilfiger says.

Mr. Hilfiger hired Mr. Som after he sought the advice of Vogue editor Anna Wintour a few years ago on how to spruce up his women's runway collection. Ms. Wintour recommended he take a look at Mr. Som. When he was looking to do similar updating with the men's runway collection in 2010, Mr. Hilfiger again went to Ms. Wintour, who suggested Mr. Spurr as one possibility. Ms. Wintour, through a spokeswoman, confirmed Mr. Hilfiger's account.

While several designers work for themselves as well as with other labels, Messrs. Som and Spurr's role with Tommy Hilfiger is uncommon. Typically, when a designer with his or her own line moonlights with a big label, the label's founder is deceased or is no longer involved. Mr. Hilfiger, 60, is very much alive and still holds the titles of visionary and principal designer.

And Mr. Hilfiger hasn't kept his business relationship with the designers under wraps in the way that bigger fashion houses usually do when they bring in smaller designers. Messrs. Som and Spurr were backstage—and were thanked in the program notes—for the women's and men's shows held during New York fashion week in February.

Robert Burke, who runs luxury-goods consultancy Robert Burke Associates, says crediting Messrs. Som and Spurr "is a smart move. It elevates [Mr. Hilfiger's] visibility and credibility in the high-end designer world."

Mr. Hilfiger says he sees hiring the men as a way to help two talented and hard-working designers. Mr. Hilfiger pays each designer a salary, which all three declined to disclose. They also get business experience working for a big fashion brand with $4.6 billion in global retail sales last year.

Mr. Hilfiger says he sees his arrangement with Messrs. Spurr and Som as an extension of his track record of breeding talent. Reed Krakoff worked at Tommy Hilfiger before being tapped by Coach, where he is executive creative director.

Many designers who are at the helm of mega-brands don't do much actual sketching and sewing, especially if their labels span a wide range of products like Mr. Hilfiger's. But even from when he started his label in 1985, Mr. Hilfiger hasn't generally been thought of as a designer who wields a sketch pad and pin cushion. Mr. Hilfiger notes he had numerous hands-on design stints early in his career.

Messrs. Som and Spurr sketch, select fabrics, make prototypes and conduct fittings for Tommy Hilfiger's runway collections. (The designers don't work on the sportswear collection that is sold exclusively at Macy's.) Last week both designers were in a factory in Italy working on prototypes for the Spring 2012 Tommy Hilfiger collection to be shown at New York fashion week in September.

The two work on their own lines at the same time. They said, in separate interviews, that they never have moments where they are conflicted about whether to save an idea for their own lines instead of using it for Hilfiger.

The process usually starts when Mr. Hilfiger conducts meetings with each designer to lay out the next collection's concept. They brainstorm, reviewing previous collections and inspirational imagery.

"They will give the initial sketch" and then work with the company's in-house design team on the details, says Mr. Hilfiger. The sketches are presented to sample makers.

"Once I sketch enough, I'll go back and get Tommy's thoughts and then he has an angle I never thought of, he adds that twist that he's known for," Mr. Spurr said by telephone from Italy. "It's a collaborative process."

"I'm there but I give them space," Mr. Hilfiger says. "If they want to try something different, I'm all for it because I like innovation and I want to see what they'll do without Big Daddy." After completing fittings of samples in Italy, Messrs. Som and Spurr present them to Mr. Hilfiger in New York to review. They coordinate with the label's stylist, Karl Templer. Mr. Hilfiger alone makes the call on what will go down the runway.