Britta Leonhardt was born in Hamburg. There she completed an apprenticeship as a tailor with Jil Sander. After that, she studied costume design with professor Dirk von Bodisco at the Hochschule für Angewandte Wissenschaften.
In 2000, she completed her assistantship at the Thalia Theatre in Hamburg and has since worked as a freelance costume designer at various German-speaking theatres.
In recent seasons, she has designed costumes for productions by Ingo Kerkhof, Dirk Schmeding, Kevin Barz, Martin Kusej, Brit Bartkowiak, Marc Becker, Karsten Wiegand, Stephan Kimmig, K.D. Schmidt, Mirja Biel, Nicolai Sykosch, Peter Hailer, Elina Finkel, Sebastian Kreyer, Jorinde Dröse and Ludger Engels, among others. She has worked as a freelance costume designer at Staatstheater Stuttgart, Konzert Theater Bern, Staatsoper Unter den Linden, Bühnen der Stadt Köln, Theater Bonn, Staatsschauspiel Dresden, Hessisches Staatstheater Wiesbaden, Staatstheater Mainz, Badisches Staatstheater Karlsruhe, Theater Luzern, Staatstheater Augsburg, Theater Heidelberg, Kampnagel Hamburg, Thalia Theater, Musiktheater im Revier, Theater Aachen, Staatstheater Braunschweig, Nationaltheater Weimar, Oldenburger Staatstheater and Münchner Volkstheater.
She also designed the costumes for the opera adaptation »Hunter‘s Bride – Der Freischütz« and for several short films.
Since 2021, Britta Leonhardt has also been working as a set designer, designing the stage for »Maria Stuart« at the Oldenburgischen Staatstheater and »Salome« at the Oper Wuppertal.