The young Croatian baritone Leon Kosavic completed his master's degree at the Music Academy in Zagreb in the singing class of Giorgio Surian, which lead to a membership of the Queen Elisabeth Music Chapel program under the direction of José van Dam.

 In 2011 he began his musical career as Papageno at the Croatian National Opera, where he sang Masetto and Moralès and Malatesta in the following years.
This was followed by important prizes for young singers at the Emmerich Smola Förderpreis, the Mirjam Helin International Singing Competition and the Stanislaw Moniuszko Competition.

Since then he has appeared at numerous European opera houses such as the Royal Opera House London (Papageno in Zauberflöte, Ping in Turandot,  Masetto in Don Giovanni), Opernhaus Zürich (Der Freischütz), La Monnaie Bruxelles (Ping in Turandot ), Theater an der Wien (Mercutio in Roméo et Juliette) Stuttgart State Opera (Don Giovanni), Liège (Figaro in Nozze di Figaro and Guglielmo in Cosi fan tutte), Antwerp (La Juive & Ariadne auf Naxos), Lausanne (Masetto in Don Giovanni), Strasbourg (Figaro in Barbiere di Siviglia) and Helsinki (Malatesta in Don Pasquale)

He was a member of the ensemble at Theater St. Gallen, where he sang Pagageno (Magic Flute) and Germont (La Traviata).

An intensive concert activity with the conductor Nathalie Stutzmann also took him to the Elbphilharmonie Hamburg, Liverpool, Sao Paolo, Bergen, Paris, London and Atlanta. Moreover, he has given concerts with the European Union Youth Symphony in the Konzerhaus Berlin and at the Grafenegg Festival.

After his debuts at the Opernhaus Zürich, Grand-Théâtre de Genève, Grand-Théâtre de Luxembourg and the Teatro Regio Torino in the last seasons, highlights in the season 25/26 include:

Die Fledermaus (Dr. Falke) at the Theater an der Wien, Don Giovanni with Riccardo Muti at the Ravenna Festival and Tokyo Spring Festival, his debut at the Dutch National Opera as Melot (Tristan und Isolde), his anticipated role debut as Escamillo (Carmen) at the Flamish Opera.