Theyskens attended École Nationale Supérieure des Arts Visuels de la Cambre in October 1994 to study fashion design.
Stylist Arianne Phillips saw photographs of his works and dressed Madonna in one of Theyskens’ black satin coatdresses for the 1998 Academy Awards.
[6][15] In November 2006, Theyskens became artistic director at Nina Ricci[1] where his focus shifted to a younger, more casual level of dressing.
[24] In 2020, Theyskens was named artistic director of Azzaro, with responsibility for the brand’s couture collections, ready-to-wear lines, and accessories for women and men; he succeeded Maxime Simoëns.
[25][26] In 2010, Assouline Publishing released a retrospective look at Theysken’s work, “The Other Side of the Picture,” which was the culmination of a 10-year collaboration with art photographer Julien Claessens.
[15] Theyskens' creations have been worn by Nicole Kidman, Cate Blanchett, Reese Witherspoon, Emma Watson, Diane Kruger, Greta Gerwig, Felicity Jones, Jennifer Aniston, Mylene Farmer, Bella Hadid and Kirsten Dunst.