Lim is of Chinese descent whose parents immigrated to the United States from Cambodia during the Cambodian genocide.

In the fall of 2005, he co-founded 3.1 Phillip Lim with friend and business partner Wen Zhou, becoming the company's creative representative.

The line's fall 2007 collection was inspired by socialite Edith Bouvier Beale and meant to embody what Lim called "pedigree minus prudence".

His spring 2010 fashion show, held on September 16, 2009, as part of the New York Fashion Week, was very well received, Lauren David Peden of Vogue reviewing the clothes as "delightfully modern, exceptionally detailed looks", "enhancing a woman’s femininity without getting all girlie-girl saccharine",[12] and Mark Holgate adding that Lim was "able to martial all the salient ideas of the season into brilliantly effortless, and wonderfully special, pieces".

[13] The collection was presented again the following day, at an exclusive runway event for American Express cardholders,[14] the designer explaining that his goal was "to provide Cardmembers insight beyond the traditional runway show and offer them a one-of-a-kind experience into the design process".

[16] The mishap triggered several articles,[17][18] and Jessica Coen of New York Magazine's The Cut even stated that "the whole thing was a catastrophe".