In 1993 he garnered wide attention when he won the BBC Cardiff Singer of the World competition and he was soon cast in several major roles in opera houses throughout Europe.
[2] His other international appearances have taken him to Germany, France, Spain, Holland, Brazil, Great Britain and the United States.
[4] In 2001, he joined Angela Gheorghiu, Daniela Barcellona, Roberto Alagna, and the Berlin Philharmonic in a production of Verdi's Requiem under the baton of Claudio Abbado.
[11] In 2005 he performed the role of Roger in Verdi's Jérusalem with conductor Paolo Olmi conducts the Netherlands Radio Symphony Orchestra and Choir.
[12] Konstantinov has spent much of his career singing roles with the Sofia National Opera where he has appeared as Mephistopheles in Gounod's Faust,[13] Raimondo in Donizetti's Lucia di Lammermoor, Count Walter in Verdi's Luisa Miller, Sparafucile in Verdi's Rigoletto, Fiesco in Verdi's Simon Boccanegra, Sarastro in Mozart's Die Zauberflöte, both Don Pedro and the title role in Mozart's Don Giovanni, and as Timur in Puccini's Turandot among other roles.