Jessica Stam was discovered in a local Tim Hortons coffee shop by Michèle Miller (an agent at the International Model Management agency in Barrie, Ontario) who found Stam on the way back from Canada's Wonderland (a theme park just outside Toronto).

Jessica Stam won the Los Angeles Model Look Search in 2002. Photographer Steven Meisel jump started her career and soon after cast her in every ad campaign of his. Suddenly, she was a star. "I guess I'm his muse," she has said. She has appeared on the cover of UK & German Vogue and she has appeared in advertisements for Marc Jacobs, Anna Sui, Vera Wang, Valentino, Miu Miu, Gucci, Prada, Dolce & Gabbana, Versace and Holt Renfrew, Dior, BCBG Maxazria, Lanvin, Roberto Cavalli, H&M, and DKNY. In 2004, Stam appeared in the short film Agent Orange.

Fashion designer Marc Jacobs created The Marc Jacobs Stam, a bag inspired by and named after her. For the Victoria's Secret Fashion Show in 2006 she opened the fourth runway theme "Pink". The appearance also included a featurette showing a Victoria’s Secret commercial shoot and what a model sees when walking the runway. In the January 2006, she appeared in the Rochas ad campaign, shot and directed by Bruno Aveillan.

For Spring 2006 Ready-to-Wear, Stam walked a total of 64 shows combined during the New York, Milan, and Paris Fashion Weeks. During Paris's Spring/Summer 2007 Haute Couture fashion week she walked for Chanel, Christian Lacroix, Christian Dior, Givenchy, and Jean Paul Gaultier. She currently stands at number four on the "Top 50 Models" rating at models.com. In the May 2007 issue of American Vogue she was featured on the cover with fellow models: Doutzen Kroes, Caroline Trentini, Raquel Zimmermann, Sasha Pivovarova, Agyness Deyn, Coco Rocha, Hilary Rhoda, Chanel Iman, and Lily Donaldson as the new crop of supermodels.

Jessica Stam modeling for Michael Kors, February 2008. Photo: Ed Kavishe, fashionwirepressIn July 2007, earning at an estimated total of $1.5 million in the past 12 months, Forbes named her fifteenth in the list of the World's 15 Top-Earning Supermodels. Currently she stars in campaigns for Bulgari, Dior, Lanvin and Escada. She also appears in the F/W 2007 Christian Dior, DKNY, Miss Sixty, Loewe and Roberto Cavalli ad campaigns. She also had campaigns for Burberry early this year. Last year in 2007 she had modelled for The Victoria's Secret runway show.