Leon Košavić began his vocal education at the age of twelve at the Academy of Music in Zagreb with Giorgio Surian. In 2011, he was awarded first prize at a Croatian national competition for students.
He made his stage debut as Moralés in Bizet's Carmen at the The Academy of Music and subsequently performed there as the Emperor in Stravinsky´s The Nightingale. He made his professional debut at the Croatian National Theatre in Zagreb as Papageno in Mozart's Die Zauberflöte, where he subsequently performed Mr. McC in Introductions and Goodbyes by Lukas Foss and Masetto in Mozart's Don Giovanni.
In 2013, he was awarded the Audience Choice Award at a competition for young artists in Croatia.