It takes more than a visionary eye for style to turn a fashion designer into a blockbuster brand. It takes a combination of right-brain creativity and left-brain execution.

For women's fashion designer Narciso Rodriguez, it has meant hiring left-brain fashion-industry veteran Robert J. Wichser in May. The label tapped him to be chief executive and resident "suit" at the 15-year-old label. Mr. Wichser's mission is to help the Narciso Rodriguez label regain the business mojo that has eluded it in recent years.

The 51-year-old Mr. Rodriguez became famous overnight as designer of the sleek silk-crepe sheath Carolyn Bessette wore to marry John F. Kennedy Jr. in September 1996. Soon after, he launched his own women's fashion line and went on to be named the Council of Fashion Designers of America's Womenswear Designer of the Year twice, in 2002 and 2003.

Mr. Wichser (pronounced "wisher"), 62, is known as a Garment District fixer, an executive who can help a creative genius get his business act together. His recent projects include stints at Sean Combs's Sean John line and at the John Varvatos label, where Mr. Wichser helped evaluate prospective partners and position the label for a sale to private investors in April.

The suit, or businessman, is recognized as indispensable to a fashion designer's survival ever since the 1960s and '70s, when Yves Saint Laurent was a pioneer of the concept of an international fashion superbrand, in large part because of guidance from his left-brain partner, Pierre Bergé. More recently, Marc Jacobs, Mr. Rodriguez's generational peer, has achieved international sales and acclaim with his own left-brain business partner, Robert Duffy.

An exacting designer, Mr. Rodriguez is known for body-conscious dresses and blouses that skim the figure with the seductive ease of a negligee. But his label has floundered in recent years, stuck in narrow distribution because it has lacked the resources and breadth of offerings that help a designer achieve fast growth at retail.

"You see the success of other designers who have the good fortune to have a solid partner on the business side. It's what I've always desired," Mr. Rodriguez said in a recent interview at his New York studio. "I needed a person to build the brand, someone to grow the company."

Accessories are the name of the game in fashion today, whether it's shoes, bags, housewares or all of the above. And high-low collaborations with retailers, like the one between Target stores and Missoni last year are also increasingly a must. Narciso Rodriguez has had very few of either.

The designer has attempted to expand, and his 2003 fragrance launch was considered a success. But partnerships with two major financial backers, AeffeSpA AEF.MI 0.00% and the former Liz Claiborne Inc., collapsed in 2006 and in 2008, respectively, over disagreements on the brand's direction.

Kathy Kalesti, currently a consultant to small designer labels, was Mr. Rodriguez's 13-year business associate, vice president of merchandising, distribution and sales and then president when she left amicably, according to both sides, about a year after the Liz Claiborne connection ended.

Mr. Rodriguez "really needed someone to objectively come in and figure out how to move the company forward," Ms. Kalesti says. "I couldn't be that and be involved in the product and the wholesale and all of that. It's too big a nut without the right infrastructure."

"It all fell on Narciso's shoulders and there wasn't an infrastructure in place to support the growth of the business," Mr. Wichser says. "There wasn't that expertise within the company."

Mr. Rodriguez tried running the business on his own and concluded he was in over his head. He reached out to Mr. Wichser, hiring him for a three-month consulting stint. The two hit it off, and Mr. Wichser's three-month engagement turned into a year. He left Narciso Rodriguez for the John Varvatos gig, but returned in May as chief executive.

Since then, Mr. Rodriguez has launched shoe and handbag lines, an e-commerce store and, in November, a lower-priced collection with Kohl's stores. Mr. Rodriguez also has signed an agreement with Gap's GPS +0.08% Banana Republic to be a fashion adviser to the chain. His third women's fragrance is expected next year.

Robert Burke, a luxury-goods consultant, said Mr. Rodriguez was wise to get into fragrances back when he did, but his label still "has to make up for lost time" by expanding.

This is a difficult time to enter the competitive accessories market, which is crowded with established brands constantly looking to broaden their price ranges and audiences, as well as younger designers who have started pumping out accessories earlier in their careers. "I hope Bob is the person to do it," Mr. Burke says.

Mr. Rodriguez says he sees Mr. Wichser as more than a suit. "I had a wealth of sketches and ideas we were showing, and they were never being brought to market," Mr. Rodriguez says. "Bob helped pull together teams to help me make those accessories a business and identify the appropriate partners to make the product."

Some of Mr. Wichser's changes met with culture shock. He instituted weekly meetings with all departments, with Mr. Rodriguez's blessing. "Design needs to be in touch with production and sales," the designer says.

At the meetings, Mr. Wichser and Mr. Rodriguez articulated their vision for the company. Previously, Mr. Rodriguez said employees had a sense of the vision, but "Bob made it crystal clear to everyone."

The designer and the CEO met with retailers to get feedback, visited factories and sat in on sales meetings. They introduced fixed deadlines and schedules for everything, including the design process, so products would arrive on retail sales floors at the start of a shipping cycle rather than weeks after it had begun. This way, more merchandise can be sold at full price, with less discounting. "That had a major impact initially on improving the business," Mr. Wichser says.

Deliveries now arrive earlier, says Daniella Vitale, chief operating officer of Barneys New York. "You can see the changes in supply-chain management."

Mr. Wichser said he made the decision to launch the shoes and handbags with Barneys, which has long carried the ready-to-wear collection, rather than a group of retailers buying small amounts here and there. He says he wanted one high-end retailer to make a significant commitment to the label in all product categories, with marketing and "real estate" on the sales floor. Barneys was willing.

Ms. Vitale says price points for the shoes "were a little higher than we would have liked," but overall Barneys has been pleased with sales of the accessories.

Narciso Rodriguez's Spring 2013 collection, shown at New York fashion week this fall, received the kind of raves the label was getting in its earliest days. But this time, the designer can't afford not to capitalize on the buzz.

Mr. Wichser said he aims to make Narciso Rodriguez "a major player in shoes and handbags," with accessories expected to become a bigger business for the label than ready-to-wear clothing. The company is looking at expanding into new areas, like eyewear, intimates, home merchandise and its own retail stores, Mr. Wichser says.

Mr. Rodriguez says he is happy so much has been accomplished in so little time. "It's great when you have someone who listens to what your vision is and makes it happen," the designer says. "There's a new energy at this company."