Gilles Montezin received his professional training at l'Ecole de la Haute Couture in Paris. After completing his studies, he went to work at l'Opera Bastille where he perfected techniques for elaborate period costuming that contribute to his craft. At the same time, he worked for both Loris Azzaro and Christian Lacroix Haute Couture and remained at Maison Lacroix for eight years. During this period, Mr. Montezin completed designs for Madonna and actresses Catherine Zeta-Jones and Monica Bellucci.

In 2004, he moved to New York City to start his own company. The designer has since had pieces filmed in "All My Children", "Guiding Light", "Ugly Betty", "PBS Live From Lincoln Center", and "Barbara Walters Special" television productions and also in the feature films "Sex and the City", and "Confessions of a Shopaholic". Celebrities he has dressed are actresses Sarah Jessica Parker, Kim Cattrall, Mary Tyler Moore, Debra Messing , Lisa Marie, news correspondents Andrea Mitchell and Courtney Hazlett, international top model Carmen Dell'Orefice, and opera singers Susan Graham and Erica Sunnegardh.

His clothes have been featured in Social Life, Elle , Women's Wear Daily, Ebony, Brilliant magazine, OK!, The New York Times,WWD, The Huffington Post, The Palm Beach Daily News and British Karen magazine ,and Papercity magazine.