Behati herself has said that she was discovered at a supermarket in Cape Town, South Africa by a photographer who asked her if she was a model. Prinsloo visited the agency a few days later and after taking some polaroids she was taken to London by Sarah Doukas, the founder of the agency Storm Model Management, where she got signed and began her career as a model.
She has appeared on the cover of Italy's Muse magazine and the British Telegraph Magazine. Also, more recently she was on the cover of Russian Vogue in February 2007, and the American Velvet magazine in June 2007. Her ad campaigns include Adore, Aquascutum, Chanel, H&M, Hugo Boss, Kurt Geiger, Marc by Marc Jacobs, Max Studio, and Nina Ricci. She has walked in fashion shows for Prada, Paul Smith, Shiatzy Chen ,Vera Wang, Marc Jacobs, Proenza Schouler, Versace, Chanel, Missoni, and DKNY.
Also on her resume are appearances in the Victoria's Secret Fashion Show in 2007, 2008, and 2009; she has also been doing print work for the company as the spokesmodel for the sub-brand Pink. In 2010, she became one of the company's Angels.
Prinsloo is ranked 31st on the Top 50 Models Women and 14th on "The Top Sexiest Models" list by models.com.
She is represented by Supreme Models in New York, Storm Models in London, Marylin Agency in Paris and D Management Group in Milan.