She grew up on her parents' horse-breeding farm in Thames, New Zealand. Having been a beauty queen, Bax was first discovered in a New Zealand shopping mall by an agent from modelling agency Clyne Model Management.
After discovering her marketing abilities as a fashion model, she soon moved to New York to work as a model. Bax became Steven Meisel's protege. With her new "boyish looks" but still very feminine, she went on to work with top photographers such as Karl Largerfeld, who treated her like his daughter, Helmut Newton and Richard Avedon.
Bax is currently married-to fashion photographer Spiros Poros and has two daughters, Lito and Dione Nefeli. Bax also has a stepson named Aris.
Bax is branching out of modeling to pursue an acting career. She appeared in the films The Big Tease and Get Over It with Kirsten Dunst.
On 3 November 2006, Bax filed a federal lawsuit in Los Angelesagainst a French men’s magazine for putting two breast-baring photos of her on its wrapper. Bax claims she did not give permission for the racy photographs, which were taken about six years ago, to be used on the front and back of Max Magazine’s April 2006 wrapper
Once discovered Bax became an international modeling success, signing with Women in New York, Marilyn in Paris, and Storm in London. She has appeared on numerous international magazine covers, including Vogue,Marie Claire, Harper's Bazaar & Mode Australia, Maxim, Vanity Fair, ELLE and Sports Illustrated. She has also appeared on more than 20 Vogue covers around the world.
In 2000, Bax joined a list of beauties like Estella Warren, Veronica Vařeková and Michelle Behennah in Sports Illustrated's Swimsuit Issue of 2000. Soon after Bax appeared in Playboy magazine in a full frontal spread.
She has appeared in campaigns for international products such as Club Monaco, Anna Sui, Clinique, Ann Taylor, DKNY, Escada, Gianfranco Ferre, Giorgio Armani, Louis Vuitton, Oscar de la Renta, Sonia Rykiel, Versace, Moschino,Nars, Valentino..
She has walked down catwalks for high fashion houses such as Moschino, Oscar de la Renta, Chanel, Christian Dior, Christian Lacroix, and Valentino, Glistening Examples, Gucci, Galliano, Donna Karan, Cynthis Rowley, Calvin Klein, Joop, Alexander McQueen, Phillip Treacy, Karl Lagerfeld, Chloe, Ralph Lauren, Prada, Miu Miu