Andrew Rosen is a pioneer in the contemporary fashion market, co-founding Theory with Elie Tahari in 1997.
Rosen sold the majority of his Theory shares in 2003 to Japan's Fast Retailing, but retains an 11 percent share and continues to run the company. He has a particularly strong relationship with Theory’s owner, Tadashi Yanai , whose company also owns Uniqlo and J Brand.
Following the sale of Theory, Rosen invested $10 million dollars in emerging designers. Rosen's portfolio of investments includes Alice + Olivia, Rag & Bone and Proenza Schouler. Rosen also has stakes in Kiki de Montparnasse, Aiko and Gryphon. By 2012, they had evolved into businesses with combined sales of over $300 million, prompting Vogue editor-in-chief Anna Wintour to say, “We don’t have a Gucci or LVMH in this country, but in his own way, Andrew is creating a kind of American equivalent.”
Rosen was arguably the first to identify the gap in the United States and international markets for fashionable contemporary brands. In response to the shifting consumer market, Rosen hired designer Olivier Theyskens , whose aesthetic was well-received in the Asian market, to head up Theory’s design team as creative director, as well as acting as creative director of the newly created Theyskens’ Theory, an advanced contemporary line. Olivier Theyskens has since left the company and the Theyskens’ Theory partnership has ended.