Her first published pictures were by Juergen Teller for a 1996 issue of i-D, and are credited with launching an ‘alternative concept of beauty’. O’Connor is noted for her angular, highly symmetrical profile and porcelain-pale complexion
She is synonymous with Charlotte Cotton’s notion of 'imperfect beauty' in 1990s fashion photography, and Karl Lagerfeld has described her as "one of the best models in the world". O’Connor has been associated with luxury labels from Chanel, Versace, Givenchy, Dolce & Gabbana, Gucci, Armani, and Jean-Paul Gaultier.
She has modelled on the catwalk for John Galliano, Christian Dior, Donna Karan, Prada, Versace, Miu Miu, Giorgio Armani, Julien MacDonald, Jean-Paul Gaultier, Badgley Mischka, Dolce & Gabbana and Ermanno Scervino among many others. She has worked with many leading fashion photographers including Patrick Demarchelier, Steven Meisel, Steven Klein, Nick Knight, Mario Testino, David Sims, and Jonathan de Villiers, and featured in magazines including Vogue, W, ELLE, Nova, Harper's Bazaar, Harpers & Queen, i-D, and Visionaire. She was on the January cover of British Vogue. In March 2003, O'Connor featured in a three-part Channel 4 documentary This Model Life.
Since 2005, she has been one of the faces of the iconic British high-street chain Marks and Spencer and in 2008 she launched the haircare line model.me for Toni & Guy alongside Jamelia and Helena Christensen.
She writes a Column for London Fashion Week paper The Daily Rubbish, currently contributes a regular blog to the online presence of British Vogue, has written for The Sunday Times and The Daily Mail and recently wrote & presented a Documentary on Fashion Erin's model world for BBC Radio 4.