Sylvette Dequest was trained in a Visual Arts school and worked as a fashion stylist for various press groups. From 1993 onwards, she devoted herself entirely to costume creation for theatre, opera and dance.
She has been working with Julie Brochen, Pierre Diot, Philippe Lanton, Jean Claude Gallotta, Omar Porras, Jean Claude Penchenat, Hélène Delavault and Jean Claude Durand, Lukas Hemleb, Claude Guerre, Bruno Boulzaguet, Benjamin Charlery, François Verret, the Company LMNO, Mitia Fodotenko, Sandy Ouvrier, David Lescot, Brigitte Seth and Roser Montlo Guberna, Jacques Osinsky, Étienne Gaudillère, Sylvain Levitte, Benjamin Guillard, Alexandre Zeff. Her cinematic work includes the costumes for Tremblez tyrans, a medium-length film by Roy Lekus and Françoise Jolivet inspired by Stendhal's childhood.
She met Thomas Jolly in 2011 and designed the costumes for Henry VI, Richard III, Thyeste, Le Dragon (Evgueni Schwartz). Her operatic work includes Fantasio (Offenbach) in 2017 at the Opéra Comique and Macbeth Underworld (Pascal Dusapin) in 2019 at La Monnaie in Brussels, which will be both revived at the Opéra Comique at the end of 2023.