One enduring image of the Obama inauguration last January was the new first lady enveloped in a shimmering white one-shouldered ball gown that bared her back and arms. The dress ended weeks of speculation over what Michelle Obama would wear that evening and launched the career of a nearly unheard-of designer, Jason Wu.

The designer hasn't wasted a bit of his Obama-induced momentum. Last January, Mr. Wu was selling his clothes in 10 stores and employed six people, and his 2008 revenues were $800,000, says Gustavo Rangel, Mr. Wu's chief financial officer and life partner. Now Jason Wu is sold in 40 stores including Saks, Neiman Marcus, Harrods in London, Lane Crawford in China and Harvey Nichols in Canada, and is on track to make $4 million in revenue this year, Mr. Rangel says. Mr. Wu has hired a personal assistant and has upped his staff to 10, with more hiring to come.

On Friday at New York's St. Regis Hotel, just two hours before showing the first collection he designed since his breakthrough, Mr. Wu worked backstage pinning and stitching a finely draped cocktail dress of black silk tulle with embroidered red hash marks—a modern sort of pointelle—onto a model. Rather than his standard uniform of Levis and Converse sneakers, Mr. Wu donned a dark Christian Dior suit. "This is Mr. Wu at the St. Regis. I'm grown up," said the featherweight 26-year-old, with the faintest grin.

With this latest collection, Mr. Wu is attempting to strike a new chord with creations more modern and sexy than the demure gowns and dresses he was known for. Aspiring to create a broad ready-to-wear brand, he has added knitwear, outerwear and more daywear, the better to fill a woman's whole closet with Jason Wu creations. "Where does my girl want to go? Ideally, I'd like to provide for her whole wardrobe," he says.

"He's really smart. He's got both the left-brain and right-brain thing going, says Robert Burke, a fashion and luxury consultant who has discussed growth plans with Mr. Wu.

Paced through a series of grand rooms in the style of Paris couture shows, Mr. Wu's collection walked a fine line between ladylike and daring. Vibrant colors and rich textures—Chanel-like tweeds and startlingly vibrant silk patterns, tweed trimmed in silk and a knitted sweater in mustard—gave punch to demure silhouettes.

There was a range of looks designed to address almost any closet conundrum, from sporty slouch-shouldered jackets over trim pants to the closing look in which model Karlie Kloss flounced down the runway in an ostrich-feathered cocktail dress. It was all wearable—wearability and breadth of offerings are the sort of things retailers are looking for these days, and Mr. Wu says he's paying attention. The show was crowded with retailers including senior executives from Saks Fifth Avenue and Bergdorf Goodman, whose presence indicates that a show is hot and expected to sell commercially.

Mr. Wu says he doesn't leave a lot of work up to design assistants. "Until the piece goes on the runway, it's got my hands on it," he says.

Born in Taiwan, Mr. Wu began designing as a child. At 16 he began designing clothing for fictional royalty: a line of Barbie-like fashion dolls for Integrity Toys Inc. that cost upwards of $100. Percy Newsum, Integrity Toy's president, credits Mr. Wu on the company's Web site with turning his firm "from a producer of mass market toys to a producer of high-end collectible dolls."

After attending Parsons School of Design and interning for designer Narciso Rodriguez, Mr. Wu launched his company three years ago. Although his first collection was purchased by Saks Fifth Avenue in 2006, it "was a rough couple of years, like all designers," says Mr. Rangel.

Then Ikram Goldman, owner of a high-fashion Chicago boutique, showed Mr. Wu's designs to Ms. Obama. Not only did she wear Jason Wu at the debut inaugural ball, she also donned his designs for the cover of Vogue (fuschia sheath dress), to the London opera (black satin overcoat) and when disembarking from a plane in London for the G-20 summit in April (chartreuse shift).

In November, Mr. Wu plans to quadruple the size of his studio, and his plans include Jason Wu stores and someday accessories such as shoes and handbags. "It's creating a lifestyle," says Mr. Rangel, using the 21st-century buzzword for big time money-making.